At 2020-10-16 08:53:00, "Hu, Jiayu" <jiayu...@intel.com> wrote:
>
>
>> -----Original Message-----
>> From: Ananyev, Konstantin <konstantin.anan...@intel.com>
>> Sent: Friday, October 16, 2020 12:16 AM
>> To: Hu, Jiayu <jiayu...@intel.com>; yang_y_yi <yang_y...@163.com>
>> Cc: dev@dpdk.org; olivier.m...@6wind.com; tho...@monjalon.net;
>> yangy...@inspur.com
>> Subject: RE: Re:RE: [PATCH] gso: fix free issue of mbuf gso segments attach
>> to
>>
>>
>>
>> >
>> > > -----Original Message-----
>> > > From: Ananyev, Konstantin <konstantin.anan...@intel.com>
>> > > Sent: Wednesday, October 14, 2020 8:06 PM
>> > > To: yang_y_yi <yang_y...@163.com>; Hu, Jiayu <jiayu...@intel.com>
>> > > Cc: dev@dpdk.org; olivier.m...@6wind.com; tho...@monjalon.net;
>> > > yangy...@inspur.com
>> > > Subject: RE: Re:RE: [PATCH] gso: fix free issue of mbuf gso segments
>> attach to
>> > >
>> > >
>> > > > From: yang_y_yi <yang_y...@163.com>
>> > > > Sent: Wednesday, October 14, 2020 3:56 AM
>> > > > To: Hu, Jiayu <jiayu...@intel.com>
>> > > > Cc: Ananyev, Konstantin <konstantin.anan...@intel.com>;
>> dev@dpdk.org;
>> > > olivier.m...@6wind.com; tho...@monjalon.net;
>> > > > yangy...@inspur.com
>> > > > Subject: Re:RE: [PATCH] gso: fix free issue of mbuf gso segments attach
>> to
>> > > >
>> > > > I think it isn't a good idea to free it in rte_gso_segment, maybe
>> application
>> > > will continue to use this pkt for other purpose, rte_gso_segment
>> > > > can't make decision for application without any notice, it is better to
>> return
>> > > this decision right backt to application.
>> > > >
>> > >
>> > > I think, if user wants to keep original packet, he can always call
>> > > rte_pktmbuf_refcnt_update(pkt, 1)
>> > > just before calling gso function.
>> > >
>> > > Also, as I remember in some cases it is not safe to do free() for input
>> packet
>> > > (as pkt_out[] can contain input pkt itself). Would it also be user
>> responsibility
>> > > to determine
>> > > such situations?
>> >
>> > In what case will pkt_out[] contain the input pkt? Can you give an example?
>>
>> As I can read the code, whenever gso code decides that
>> no segmentation is not really needed, or it is not capable
>> of doing it properly.
>> Let say:
>>
>> gso_tcp4_segment(struct rte_mbuf *pkt,
>> uint16_t gso_size,
>> uint8_t ipid_delta,
>> struct rte_mempool *direct_pool,
>> struct rte_mempool *indirect_pool,
>> struct rte_mbuf **pkts_out,
>> uint16_t nb_pkts_out)
>> {
>> ...
>> /* Don't process the fragmented packet */
>> ipv4_hdr = (struct rte_ipv4_hdr *)(rte_pktmbuf_mtod(pkt, char *) +
>> pkt->l2_len);
>> frag_off = rte_be_to_cpu_16(ipv4_hdr->fragment_offset);
>> if (unlikely(IS_FRAGMENTED(frag_off))) {
>> pkts_out[0] = pkt;
>> return 1;
>> }
>>
>> /* Don't process the packet without data */
>> hdr_offset = pkt->l2_len + pkt->l3_len + pkt->l4_len;
>> if (unlikely(hdr_offset >= pkt->pkt_len)) {
>> pkts_out[0] = pkt;
>> return 1;
>> }
>>
>> That's why in rte_gso_segment() we update refcnt only when ret > 1.
>
>But in these cases, the value of ret is 1. So we can free input pkt only when
>ret > 1. Like:
>
>- if (ret > 1) {
>- pkt_seg = pkt;
>- while (pkt_seg) {
>- rte_mbuf_refcnt_update(pkt_seg, -1);
>- pkt_seg = pkt_seg->next;
>- }
>- } else if (ret < 0) {
>+ if (ret > 1)
>+ rte_pktmbuf_free(pkt);
>+ else if (ret < 0) {
> /* Revert the ol_flags in the event of failure. */
> pkt->ol_flags = ol_flags;
> }
>
>Thanks,
>Jiayu
>>
>>
>>
Jiayu, please help commit the patch you pasted if you think it is ok. I need to
update my GSO patch based on this fix, thanks a lot.
