netdev - Re: [PATCH v3 2/7] net: Use skb accessors in network core

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Message-ID: <20190723111755.GI363@bombadil.infradead.org>
Date:   Tue, 23 Jul 2019 04:17:55 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Yunsheng Lin <linyunsheng@...wei.com>
Cc:     davem@...emloft.net, hch@....de, netdev@...r.kernel.org
Subject: Re: [PATCH v3 2/7] net: Use skb accessors in network core

On Tue, Jul 23, 2019 at 11:56:41AM +0800, Yunsheng Lin wrote:
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index 6f1e31f674a3..e32081709a0d 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -2975,11 +2975,15 @@ skb_zerocopy(struct sk_buff *to, struct sk_buff *from, int len, int hlen)
> >  	skb_zerocopy_clone(to, from, GFP_ATOMIC);
> >  
> >  	for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {
> > +		int size;
> > +
> >  		if (!len)
> >  			break;
> >  		skb_shinfo(to)->frags[j] = skb_shinfo(from)->frags[i];
> > -		skb_shinfo(to)->frags[j].size = min_t(int, skb_shinfo(to)->frags[j].size, len);
> > -		len -= skb_shinfo(to)->frags[j].size;
> > +		size = min_t(int, skb_frag_size(&skb_shinfo(to)->frags[j]),
> > +					len);
> 
> It seems skb_frag_size returns unsigned int here, maybe:
> 
> unsigned int size;
> 
> size = min_t(unsigned int, skb_frag_size(&skb_shinfo(to)->frags[j]),
> 
> The original code also do not seem to using the correct min_t, but
> perhaps it is better to clean that up too?

A signed size also doesn't make sense to me, but I wasn't sufficiently
certain to make that change.  Please feel free to send a followup patch
for people to consider.