linux-kernel - Re: [PATCH v2 net-next 05/15] net: sgi: ioc3-eth: allocate space for desc rings only once

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Date:   Thu, 29 Aug 2019 15:05:04 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Thomas Bogendoerfer <tbogendoerfer@...e.de>
Cc:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 05/15] net: sgi: ioc3-eth: allocate space
 for desc rings only once

On Fri, 30 Aug 2019 00:00:58 +0200, Thomas Bogendoerfer wrote:
> On Thu, 29 Aug 2019 14:05:37 -0700
> Jakub Kicinski <jakub.kicinski@...ronome.com> wrote:
> 
> > On Thu, 29 Aug 2019 17:50:03 +0200, Thomas Bogendoerfer wrote:  
> > > +		if (skb)
> > > +			dev_kfree_skb_any(skb);  
> > 
> > I think dev_kfree_skb_any() accepts NULL  
> 
> yes, I'll drop the if
> 
> > > +
> > > +	/* Allocate and rx ring.  4kb = 512 entries  */
> > > +	ip->rxr = (unsigned long *)get_zeroed_page(GFP_ATOMIC);
> > > +	if (!ip->rxr) {
> > > +		pr_err("ioc3-eth: rx ring allocation failed\n");
> > > +		err = -ENOMEM;
> > > +		goto out_stop;
> > > +	}
> > > +
> > > +	/* Allocate tx rings.  16kb = 128 bufs.  */
> > > +	ip->txr = (struct ioc3_etxd *)__get_free_pages(GFP_KERNEL, 2);
> > > +	if (!ip->txr) {
> > > +		pr_err("ioc3-eth: tx ring allocation failed\n");
> > > +		err = -ENOMEM;
> > > +		goto out_stop;
> > > +	}  
> > 
> > Please just use kcalloc()/kmalloc_array() here,  
> 
> both allocation will be replaced in patch 11 with dma_direct_alloc_pages.
> So I hope I don't need to change it here.

Ah, missed that!

> Out of curiosity does kcalloc/kmalloc_array give me the same guarantees about
> alignment ? rx ring needs to be 4KB aligned, tx ring 16KB aligned.

I don't think so, actually, I was mostly worried you are passing
address from get_page() into kfree() here ;) But patch 11 cures that,
so that's good, too.

> >, and make sure the flags
> > are set to GFP_KERNEL whenever possible. Here and in ioc3_alloc_rings()
> > it looks like GFP_ATOMIC is unnecessary.  
> 
> yes, I'll change it