At 2020-10-26 10:06:09, "Jiayu Hu" <jiayu...@intel.com> wrote: >On Mon, Oct 26, 2020 at 08:57:30AM +0800, yang_y_yi wrote: >> At 2020-10-23 22:46:42, "Ananyev, Konstantin" <konstantin.anan...@intel.com> >> wrote: >> >> >> From: yang_y_yi <yang_y...@163.com> >> >> Sent: Friday, October 23, 2020 2:18 PM >> >> To: Ananyev, Konstantin <konstantin.anan...@intel.com> >> >> Cc: dev@dpdk.org; Hu, Jiayu <jiayu...@intel.com>; techbo...@dpdk.org; >> >> tho...@monjalon.net; yangy...@inspur.com >> >> Subject: Re:RE: [PATCH v2] gso: fix free issue of mbuf gso segments >> >> attach to >> >> >> >> Konstantin, thank you so much for comments, my replies inline, please >> >> check them. >> >> At 2020-10-22 21:16:43, "Ananyev, Konstantin" >> >> <mailto:konstantin.anan...@intel.com> wrote: >> >> > >> >> >> >> >> >> rte_gso_segment decreased refcnt of pkt by one, but >> >> >> it is wrong if pkt is external mbuf, pkt won't be >> >> >> freed because of incorrect refcnt, the result is >> >> >> application can't allocate mbuf from mempool because >> >> >> mbufs in mempool are run out of. >> >> >> >> >> >> One correct way is application should call >> >> >> rte_pktmbuf_free after calling rte_gso_segment to free >> >> >> pkt explicitly. rte_gso_segment mustn't handle it, this >> >> >> should be responsibility of application. >> >> > >> >> >Probably needs to be stated clearly: >> >> >It is a change in functional behaviour. >> >> >Without deprecation note in advance. >> >> >> >> Ok, I'll add such statement in next version. >> >> >> >> >TB members: please provide your opinion on that patch. >> >> > >> >> >> >> >> >> Fixes: 119583797b6a ("gso: support TCP/IPv4 GSO") >> >> >> Signed-off-by: Yi Yang <mailto:yangy...@inspur.com> >> >> >> --- >> >> >> Changelog: >> >> >> >> >> >> v1->v2: >> >> >> - update description of rte_gso_segment(). >> >> >> - change code which calls rte_gso_segment() to >> >> >> fix free issue. >> >> >> >> >> >> --- >> >> >> app/test-pmd/csumonly.c | 3 ++- >> >> >> doc/guides/prog_guide/generic_segmentation_offload_lib.rst | 7 +++++-- >> >> > >> >> >I think release notes also have to be updated. >> >> >> >> Ok, also will update it to reflect this change. >> >> >> >> > >> >> >> lib/librte_gso/rte_gso.c | 9 >> >> >> +-------- >> >> >> lib/librte_gso/rte_gso.h | 7 +++++-- >> >> >> 4 files changed, 13 insertions(+), 13 deletions(-) >> >> >> >> >> >> diff --git a/app/test-pmd/csumonly.c b/app/test-pmd/csumonly.c >> >> >> index 3d7d244..829e07f 100644 >> >> >> --- a/app/test-pmd/csumonly.c >> >> >> +++ b/app/test-pmd/csumonly.c >> >> >> @@ -1080,11 +1080,12 @@ struct simple_gre_hdr { >> >> >> ret = rte_gso_segment(pkts_burst[i], gso_ctx, >> >> >> &gso_segments[nb_segments], >> >> >> GSO_MAX_PKT_BURST - nb_segments); >> >> >> + /* pkts_burst[i] can be freed safely here. */ >> >> >> + rte_pktmbuf_free(pkts_burst[i]); >> >> > >> >> >It doesn't look correct to me. >> >> >I think it should be: >> >> >If (ret > 1) rte_pktmbuf_free(pkts_burst[i]); >> >> >> >> No, in original implementation, if gso failed, application will free it, >> >> otherwise rte_gso_segment will free it (i.e. refcnt update -1 in >> >> rte_gso_segment), this change will change previous behavior. application >> >> will free it for both cases. >> > >> > >> >That's the point - with current implementation: >> >If ret == 1, then you shouldn't free input packet. >> >Because in that case: >> >input_pkt == output_pkt[0] >> > >> >And if you'll free it, you can't use it after it. >> >In that particular case, you can't TX it. >> >> I checked gso code again, there are two cases even if ret == 1, one case is >> it isn't segmented, the other is it is segmented but gso_do_segment returns >> 1, for case #1, we can handle it as you said, but for case #2, we can't >> handle it as you said because it has been segmented in fact. So I think we >> should return 0 foe case #1 and don't do assignment "pkts_out[0] = pkt;", >> we should handle case #2 as before, right? >> > >When will #2 case happen? In current implementation, >ret of gso_do_segment() is > 1, when GSO happens; otherwise, >ret is negative. It doesn't return 1. If you mean the >case that pkt_len is smaller than gso_size, gso_do_segment() >will not be called, since rte_gso_segment() will compare >pkt_len and gso_size before. > >Thanks, >Jiayu
Got it, thanks Jiayu, I'll send out v3 to fix all the comments. Is "return 0 for the case ret == 1" ok? Before, this is still transmitted as a normal packet, but it is dropped/freed if ret <0. >> > >> >> >> >> >> >> >>
