Re: [PATCH net-next v3] net: mana: Allow variable size indirection table

[Shradha Gupta]

On Tue, Jun 04, 2024 at 10:33:49AM +0100, Simon Horman wrote:
> On Fri, May 31, 2024 at 08:37:41AM -0700, Shradha Gupta wrote:
> > Allow variable size indirection table allocation in MANA instead
> > of using a constant value MANA_INDIRECT_TABLE_SIZE.
> > The size is now derived from the MANA_QUERY_VPORT_CONFIG and the
> > indirection table is allocated dynamically.
> > 
> > Signed-off-by: Shradha Gupta <shradhagupta@xxxxxxxxxxxxxxxxxxx>
> > Reviewed-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> > Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> 
> ...
> 
> > diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> 
> ...
> 
> > @@ -2344,11 +2352,33 @@ static int mana_create_vport(struct mana_port_context *apc,
> >  	return mana_create_txq(apc, net);
> >  }
> >  
> > +static int mana_rss_table_alloc(struct mana_port_context *apc)
> > +{
> > +	if (!apc->indir_table_sz) {
> > +		netdev_err(apc->ndev,
> > +			   "Indirection table size not set for vPort %d\n",
> > +			   apc->port_idx);
> > +		return -EINVAL;
> > +	}
> > +
> > +	apc->indir_table = kcalloc(apc->indir_table_sz, sizeof(u32), GFP_KERNEL);
> > +	if (!apc->indir_table)
> > +		return -ENOMEM;
> > +
> > +	apc->rxobj_table = kcalloc(apc->indir_table_sz, sizeof(mana_handle_t), GFP_KERNEL);
> > +	if (!apc->rxobj_table) {
> > +		kfree(apc->indir_table);
> 
> Hi, Shradha
> 
> Perhaps I am on the wrong track here, but I have some concerns
> about clean-up paths.
> 
> Firstly.  I think that apc->indir_table should be to NULL here for
> consistency with other clean-up paths. Or alternatively, fields of apc
> should not set to NULL elsewhere after being freed.

Hi Simon,

Thanks for the comments. This makes sense, I am planning of consistently removing
the NULLify from other places too as per Leon's comments.
> 
> In looking into this I noticed that mana_probe() does not call
> mana_remove() or return an error in the cases where mana_probe_port() or
> mana_attach() fail unless add_adev also fails. If so, is that intentional?

Right, so most calls like mana_probe_port(), mana_attach() cleanup after themselves
in the code if there is any error. So, not having to call mana_remove() in these
cases in mana_probe() is intentional. But I do agree that an error is returned in
mana_probe() only if add_adev also fails. I'll fix that too in the next version
> 
> In any case, I would suggest as a follow-up, arranging things so that when
> an error occurs in a function, anything that was allocated is unwound
> before returning an error.
> 
> I think this would make allocation/deallocation easier to reason with.
> And I suspect it would avoid both the need for fields of structures to be
> zeroed after being freed, and the need to call mana_remove() from
> mana_probe().

Agreed
> 
> > +		return -ENOMEM;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> >  static void mana_rss_table_init(struct mana_port_context *apc)
> >  {
> >  	int i;
> >  
> > -	for (i = 0; i < MANA_INDIRECT_TABLE_SIZE; i++)
> > +	for (i = 0; i < apc->indir_table_sz; i++)
> >  		apc->indir_table[i] =
> >  			ethtool_rxfh_indir_default(i, apc->num_queues);
> >  }
> 
> ...
> 
> > @@ -2739,11 +2772,17 @@ static int mana_probe_port(struct mana_context *ac, int port_idx,
> >  	err = register_netdev(ndev);
> >  	if (err) {
> >  		netdev_err(ndev, "Unable to register netdev.\n");
> > -		goto reset_apc;
> > +		goto free_indir;
> >  	}
> >  
> >  	return 0;
> >  
> > +free_indir:
> > +	apc->indir_table_sz = 0;
> > +	kfree(apc->indir_table);
> > +	apc->indir_table = NULL;
> > +	kfree(apc->rxobj_table);
> > +	apc->rxobj_table = NULL;
> >  reset_apc:
> >  	kfree(apc->rxqs);
> >  	apc->rxqs = NULL;
> 
> nit: Not strictly related to this patch, but the reset_apc code should
>      probably be a call to mana_cleanup_port_context() as it is the dual of
>      mana_init_port_context() which is called earlier in mana_probe_port()

Sure, let me do that too.
> 
> ...
> 
> > @@ -2931,6 +2972,11 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
> >  		}
> >  
> >  		unregister_netdevice(ndev);
> > +		apc->indir_table_sz = 0;
> > +		kfree(apc->indir_table);
> > +		apc->indir_table = NULL;
> > +		kfree(apc->rxobj_table);
> > +		apc->rxobj_table = NULL;
> 
> The code to free and zero indir_table_sz and indir_table appears twice
> in this patch. Perhaps a helper to do this, which would be the dual
> of mana_rss_table_alloc is in order.
Makes sense, will change this too.

Thanks,
Shradha.
> 
> >  
> >  		rtnl_unlock();
> >  
> 
> ...