Subject: Re: [PATCH net v3 2/4] flow_offload: fix incorrect cb_priv check for flow_block_cb

From: Simon Horman <[email-masked]>
Date: Tue, 16 Jun 2020 16:34:28 +0200

On Tue, Jun 16, 2020 at 10:20:46PM +0800, wenxu wrote:
> 
> 在 2020/6/16 18:51, Simon Horman 写道:
> > On Tue, Jun 16, 2020 at 11:19:38AM +0800, [email-masked] wrote:
> >> From: wenxu <[email-masked]>
> >>
> >> In the function __flow_block_indr_cleanup, The match stataments
> >> this->cb_priv == cb_priv is always false, the flow_block_cb->cb_priv
> >> is totally different data with the flow_indr_dev->cb_priv.
> >>
> >> Store the representor cb_priv to the flow_block_cb->indr.cb_priv in
> >> the driver.
> >>
> >> Fixes: 1fac52da5942 ("net: flow_offload: consolidate indirect flow_block infrastructure")
> >> Signed-off-by: wenxu <[email-masked]>
> > Hi Wenxu,
> >
> > I wonder if this can be resolved by using the cb_ident field of struct
> > flow_block_cb.
> >
> > I observe that mlx5e_rep_indr_setup_block() seems to be the only call-site
> > where the value of the cb_ident parameter of flow_block_cb_alloc() is
> > per-block rather than per-device. So part of my proposal is to change
> > that.
> 
> I check all the xxdriver_indr_setup_block. It seems all the cb_ident parameter of
> 
> flow_block_cb_alloc is per-block. Both in the nfp_flower_setup_indr_tc_block
> 
> and bnxt_tc_setup_indr_block.
> 
> 
> nfp_flower_setup_indr_tc_block:
> 
> struct nfp_flower_indr_block_cb_priv *cb_priv;
> 
> block_cb = flow_block_cb_alloc(nfp_flower_setup_indr_block_cb,
>                                                cb_priv, cb_priv,
>                                                nfp_flower_setup_indr_tc_release);
> 
> 
> bnxt_tc_setup_indr_block:
> 
> struct bnxt_flower_indr_block_cb_priv *cb_priv;
> 
> block_cb = flow_block_cb_alloc(bnxt_tc_setup_indr_block_cb,
>                                                cb_priv, cb_priv,
>                                                bnxt_tc_setup_indr_rel);
> 
> 
> And the function flow_block_cb_is_busy called in most place. Pass the
> 
> parameter as cb_priv but not cb_indent .

Thanks, I see that now. But I still think it would be useful to understand
the purpose of cb_ident. It feels like it would lead to a clean solution
to the problem you have highlighted.

> > The other part of my proposal is to make use of cb_ident in
> > __flow_block_indr_cleanup(). Which does seem to match the intended
> > purpose of cb_ident. Perhaps it would also be good to document what
> > the intended purpose of cb_ident (and the other fields of struct
> > flow_block_cb) is.
> >
> > Compile tested only.
> >
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/rep/tc.c b/drivers/net/ethernet/mellanox/mlx5/core/en/rep/tc.c
> > index a62bcf0cf512..4de6fcae5252 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/en/rep/tc.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/rep/tc.c
> > @@ -438,7 +438,7 @@ mlx5e_rep_indr_setup_block(struct net_device *netdev,
> >  		list_add(&indr_priv->list,
> >  			 &rpriv->uplink_priv.tc_indr_block_priv_list);
> >  
> > -		block_cb = flow_block_cb_alloc(setup_cb, indr_priv, indr_priv,
> > +		block_cb = flow_block_cb_alloc(setup_cb, rpriv, indr_priv,
> >  					       mlx5e_rep_indr_block_unbind);
> >  		if (IS_ERR(block_cb)) {
> >  			list_del(&indr_priv->list);
> > diff --git a/net/core/flow_offload.c b/net/core/flow_offload.c
> > index b288d2f03789..d281fb182894 100644
> > --- a/net/core/flow_offload.c
> > +++ b/net/core/flow_offload.c
> > @@ -373,14 +373,13 @@ int flow_indr_dev_register(flow_indr_block_bind_cb_t *cb, void *cb_priv)
> >  EXPORT_SYMBOL(flow_indr_dev_register);
> >  
> >  static void __flow_block_indr_cleanup(void (*release)(void *cb_priv),
> > -				      void *cb_priv,
> > +				      void *cb_ident,
> >  				      struct list_head *cleanup_list)
> >  {
> >  	struct flow_block_cb *this, *next;
> >  
> >  	list_for_each_entry_safe(this, next, &flow_block_indr_list, indr.list) {
> > -		if (this->release == release &&
> > -		    this->cb_priv == cb_priv) {
> > +		if (this->release == release && this->cb_ident == cb_ident) {
> >  			list_move(&this->indr.list, cleanup_list);
> >  			return;
> >  		}
> >