RE: [PATCH net-next 1/2] devlink: unify devlink_shd_get_priv() into devlink_priv()

["Loktionov, Aleksandr" <aleksandr.loktionov@intel.com>]

> -----Original Message-----
> From: Kitszel, Przemyslaw <przemyslaw.kitszel@intel.com>
> Sent: Wednesday, March 25, 2026 7:27 AM
> To: Jiri Pirko <jiri@resnulli.us>; netdev@vger.kernel.org; Jakub
> Kicinski <kuba@kernel.org>
> Cc: Nguyen, Anthony L <anthony.l.nguyen@intel.com>; intel-wired-
> lan@lists.osuosl.org; Loktionov, Aleksandr
> <aleksandr.loktionov@intel.com>; edumazet@google.com;
> horms@kernel.org; pabeni@redhat.com; davem@davemloft.net; Schmidt,
> Michal <mschmidt@redhat.com>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@intel.com>
> Subject: [PATCH net-next 1/2] devlink: unify devlink_shd_get_priv()
> into devlink_priv()
> 
> Unify access API to shared devlink priv data with normal devlink.
> 
> Thanks to Jiri Pirko, we now have ability to create shared devlink
> instances [1]. Introduction series have added usage of those for mlx,
> but without priv data attached to the shared devlink.
> 
> Current API makes it possible to access shared devlink instance's priv
> data:
> 
> 	void *devlink_shd_get_priv(struct devlink *devlink);
> 
> but it is easy to forget (especially during rebase from "before shared
> devlinks" era) and call:
> 
> 	void *devlink_priv(struct devlink *devlink);
> 
> which even has the same signature, so it's hard to catch the error.
> 
> New proposed API unifies both calls into one, without any increase in
> the observed struct size. (Alternative could be to store additional
> pointer, set during devlink_alloc).
> 
> Unexport the less convenient API call.
> 
> [1] commit 411ad0605875 ("Merge branch 'devlink-introduce-shared-
> devlink-instance-for-pfs-on-same-chip'")
> [1] https://lore.kernel.org/all/20260312100407.551173-1-
> jiri@resnulli.us
> 
> Signed-off-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
> ---
> v1:
> https://lore.kernel.org/netdev/20260323132136.13191-1-
> przemyslaw.kitszel@intel.com
> 
> v2:
> - fix typos (Alex, Jiri)
> - fix infinite recurrence (Alex)
> - add __devlink_priv(), which is more general than v1's
> devlink_to_shd()
>   (Jiri)
> ---
>  net/devlink/devl_internal.h |  7 +++++++
>  net/devlink/core.c          | 10 +++++++++-
>  net/devlink/sh_dev.c        |  8 ++++----
>  3 files changed, 20 insertions(+), 5 deletions(-)
> 
> diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
> index 7dfb7cdd2d23..0a57318d92f8 100644
> --- a/net/devlink/devl_internal.h
> +++ b/net/devlink/devl_internal.h
> @@ -58,6 +58,7 @@ struct devlink {
>  	struct mutex lock;
>  	struct lock_class_key lock_key;
>  	u8 reload_failed:1;
> +	u8 is_shd:1;
>  	refcount_t refcount;
>  	struct rcu_work rwork;
>  	struct devlink_rel *rel;
> @@ -72,6 +73,12 @@ struct devlink *__devlink_alloc(const struct
> devlink_ops *ops, size_t priv_size,
>  				struct net *net, struct device *dev,
>  				const struct device_driver *dev_driver);
> 
> +/* Get priv allocated for struct devlink */ void
> *__devlink_priv(struct
> +devlink *devlink);
> +
> +/* Get private data from shared devlink instance */ void
> +*devlink_shd_get_priv(struct devlink *devlink);
> +
>  #define devl_warn(devlink, format, args...)				\
>  	do {								\
>  		if ((devlink)->dev)					\
> diff --git a/net/devlink/core.c b/net/devlink/core.c index
> eeb6a71f5f56..a242be203fe8 100644
> --- a/net/devlink/core.c
> +++ b/net/devlink/core.c
> @@ -230,10 +230,18 @@ int devlink_rel_devlink_handle_put(struct
> sk_buff *msg, struct devlink *devlink,
>  	return err;
>  }
> 
> -void *devlink_priv(struct devlink *devlink)
> +void *__devlink_priv(struct devlink *devlink)
>  {
>  	return &devlink->priv;
>  }
> +
> +void *devlink_priv(struct devlink *devlink) {
> +	if (devlink->is_shd)
> +		return devlink_shd_get_priv(devlink);
> +
> +	return __devlink_priv(devlink);
> +}
>  EXPORT_SYMBOL_GPL(devlink_priv);
> 
>  struct devlink *priv_to_devlink(void *priv) diff --git
I'm worried about priv_to_devlink(), if someone passes the result of devlink_priv(shared_dl) as priv,
container_of computes garbage - because the pointer came from shd->priv, NOT from &devlink->priv.


...


> 
>  	return shd->priv;
>  }
> -EXPORT_SYMBOL_GPL(devlink_shd_get_priv);
> --
> 2.51.1