On 3/19/18 10:30 PM, Yuan, Linyu (NSB - CN/Shanghai) wrote:
-----Original Message-----
From: netdev-ow...@vger.kernel.org [mailto:netdev-ow...@vger.kernel.org]
On Behalf Of Yonghong Song
Sent: Tuesday, March 20, 2018 1:16 PM
To: eduma...@google.com; a...@fb.com; dan...@iogearbox.net;
dipt...@fb.com; netdev@vger.kernel.org
Cc: kernel-t...@fb.com
Subject: [PATCH net-next 1/2] net: permit skb_segment on head_frag frag_list
skb
while (pos < offset + len) {
if (i >= nfrags) {
- BUG_ON(skb_headlen(list_skb));
+ if (skb_headlen(list_skb) && check_list_skb ==
list_skb) {
Here cause next BUG_ON always false.
The idea is since in this branch, we did not do list_skb =
list_skb->next. So we update check_list_skb. Next time, when the
control reaches here, list_skb may still be the same, but check_list_skb
is not, so we proceed to process list_skb->frags in the else branch.
In the else branch, we have
list_skb = list_skb->next;
check_list_skb = list_skb;
So when the current frags are processed and ready for the list_skb.
list_skb will be equal to check_list_skb and it will be processed again.
It is a little bit convoluted. Please let me know you have better idea.
+ } else {
+ BUG_ON(skb_headlen(list_skb) &&
check_list_skb ==
list_skb);
Just according code logic, no need BUG_ON, right?
Oh, yes, we do not need this. Will remove in the next version.
- i = 0;
- nfrags = skb_shinfo(list_skb)->nr_frags;
- frag = skb_shinfo(list_skb)->frags;
- frag_skb = list_skb;
+ i = 0;
+ nfrags = skb_shinfo(list_skb)->nr_frags;
+ frag = skb_shinfo(list_skb)->frags;
+ frag_skb = list_skb;
- BUG_ON(!nfrags);
+ BUG_ON(!nfrags);
- if (skb_orphan_frags(frag_skb, GFP_ATOMIC) ||
- skb_zerocopy_clone(nskb, frag_skb,
- GFP_ATOMIC))
- goto err;
+ if (skb_orphan_frags(frag_skb,
GFP_ATOMIC) ||
+ skb_zerocopy_clone(nskb, frag_skb,
GFP_ATOMIC))
+ goto err;
- list_skb = list_skb->next;
+ list_skb = list_skb->next;
+ check_list_skb = list_skb;
+ }
}
if (unlikely(skb_shinfo(nskb)->nr_frags >=
--
2.9.5
