Subject: Re: [ovs-dev] [RFC PATCH 1/7] net: openvswitch: Move NSH buffer out of do_execute_actions

From: "Nicholas Piggin" <[email-masked]>
Date: Wed, 27 Sep 2023 20:03:58 +1000

On Wed Sep 27, 2023 at 6:26 PM AEST, Ilya Maximets wrote:
> On 9/27/23 02:13, Nicholas Piggin wrote:
> > This takes do_execute_actions stack use from 544 bytes to 288
> > bytes. execute_push_nsh uses 336 bytes, but it is a leaf call not
> > involved in recursion.
> > 
> > Signed-off-by: Nicholas Piggin <[email-masked]>
> > ---
> >  net/openvswitch/actions.c | 27 +++++++++++++++++----------
> >  1 file changed, 17 insertions(+), 10 deletions(-)
>
> Hi, Nicholas.  I made the same change about a week ago:
>   https://lore.kernel.org/netdev/[email-masked]/
> So, you can drop this patch from your set.

Ah nice, I didn't see it. Looks good to me.

Thanks,
Nick

>
> Best regards, Ilya Maximets.
>
> > 
> > diff --git a/net/openvswitch/actions.c b/net/openvswitch/actions.c
> > index fd66014d8a76..8933caa92794 100644
> > --- a/net/openvswitch/actions.c
> > +++ b/net/openvswitch/actions.c
> > @@ -1286,6 +1286,21 @@ static int execute_dec_ttl(struct sk_buff *skb, struct sw_flow_key *key)
> >  	return 0;
> >  }
> >  
> > +static noinline_for_stack int execute_push_nsh(struct sk_buff *skb,
> > +					       struct sw_flow_key *key,
> > +					       const struct nlattr *attr)
> > +{
> > +	u8 buffer[NSH_HDR_MAX_LEN];
> > +	struct nshhdr *nh = (struct nshhdr *)buffer;
> > +	int err;
> > +
> > +	err = nsh_hdr_from_nlattr(attr, nh, NSH_HDR_MAX_LEN);
> > +	if (likely(!err))
> > +		err = push_nsh(skb, key, nh);
> > +
> > +	return err;
> > +}
> > +
> >  /* Execute a list of actions against 'skb'. */
> >  static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> >  			      struct sw_flow_key *key,
> > @@ -1439,17 +1454,9 @@ static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
> >  			err = pop_eth(skb, key);
> >  			break;
> >  
> > -		case OVS_ACTION_ATTR_PUSH_NSH: {
> > -			u8 buffer[NSH_HDR_MAX_LEN];
> > -			struct nshhdr *nh = (struct nshhdr *)buffer;
> > -
> > -			err = nsh_hdr_from_nlattr(nla_data(a), nh,
> > -						  NSH_HDR_MAX_LEN);
> > -			if (unlikely(err))
> > -				break;
> > -			err = push_nsh(skb, key, nh);
> > +		case OVS_ACTION_ATTR_PUSH_NSH:
> > +			err = execute_push_nsh(skb, key, nla_data(a));
> >  			break;
> > -		}
> >  
> >  		case OVS_ACTION_ATTR_POP_NSH:
> >  			err = pop_nsh(skb, key);