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From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: "Hu, Jiayu" <jiayu.hu@intel.com>,
	"yang_y_yi@163.com" <yang_y_yi@163.com>,
	 "dev@dpdk.org" <dev@dpdk.org>
Cc: "mark.b.kavanagh@intel.com" <mark.b.kavanagh@intel.com>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"thomas@monjalon.net" <thomas@monjalon.net>,
	"yangyi01@inspur.com" <yangyi01@inspur.com>
Subject: Re: [dpdk-dev] [PATCH] gso: fix free issue of mbuf gso segments attach to
Date: Tue, 13 Oct 2020 15:39:20 +0000
Message-ID: <BYAPR11MB3301BB7E22FF7268741D094F9A040@BYAPR11MB3301.namprd11.prod.outlook.com> (raw)
In-Reply-To: <43f71e6c9d2f4d5ba3ab56a921c5912d@intel.com>


> > 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.
> 
> GSO doesn't support the input pktmbuf has external buffer.
> Indeed, requiring users to free the input pktmbuf can avoid
> memory leak, but I'm afraid that it also changes the semantic
> of rte_gso_segment() which is defined in rte_gso.h.
> 
> @Konstantin, any suggestions?

Probably, a stupid question, but why can't we call mbuf_free()
here instead fo decrementing refcnt manually:
if (ret > 1)
	rte_pktmbuf_free(pkt);
else if ...
?



> 
> Thanks,
> Jiayu
> >
> > Fixes: 119583797b6a ("gso: support TCP/IPv4 GSO")
> > Signed-off-by: Yi Yang <yangyi01@inspur.com>
> > ---
> >  doc/guides/prog_guide/generic_segmentation_offload_lib.rst | 7 +++++--
> >  lib/librte_gso/rte_gso.c                                   | 9 +--------
> >  2 files changed, 6 insertions(+), 10 deletions(-)
> >
> > diff --git a/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
> > b/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
> > index 205cb8a..8577572 100644
> > --- a/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
> > +++ b/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
> > @@ -25,8 +25,9 @@ Bearing that in mind, the GSO library enables DPDK
> > applications to segment
> >  packets in software. Note however, that GSO is implemented as a
> > standalone
> >  library, and not via a 'fallback' mechanism (i.e. for when TSO is unsupported
> >  in the underlying hardware); that is, applications must explicitly invoke the
> > -GSO library to segment packets. The size of GSO segments ``(segsz)`` is
> > -configurable by the application.
> > +GSO library to segment packets, they also must call ``rte_pktmbuf_free()`` to
> > +free mbuf GSO segments attach to after calling ``rte_gso_segment()``. The
> > size
> > +of GSO segments ``(segsz)`` is configurable by the application.
> >
> >  Limitations
> >  -----------
> > @@ -233,6 +234,8 @@ To segment an outgoing packet, an application must:
> >
> >  #. Invoke the GSO segmentation API, ``rte_gso_segment()``.
> >
> > +#. Call ``rte_pktmbuf_free()`` to free mbuf ``rte_gso_segment()`` segments.
> > +
> >  #. If required, update the L3 and L4 checksums of the newly-created
> > segments.
> >     For tunneled packets, the outer IPv4 headers' checksums should also be
> >     updated. Alternatively, the application may offload checksum calculation
> > diff --git a/lib/librte_gso/rte_gso.c b/lib/librte_gso/rte_gso.c
> > index 751b5b6..0d6cae5 100644
> > --- a/lib/librte_gso/rte_gso.c
> > +++ b/lib/librte_gso/rte_gso.c
> > @@ -30,7 +30,6 @@
> >  uint16_t nb_pkts_out)
> >  {
> >  struct rte_mempool *direct_pool, *indirect_pool;
> > -struct rte_mbuf *pkt_seg;
> >  uint64_t ol_flags;
> >  uint16_t gso_size;
> >  uint8_t ipid_delta;
> > @@ -80,13 +79,7 @@
> >  return 1;
> >  }
> >
> > -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 < 0) {
> >  /* Revert the ol_flags in the event of failure. */
> >  pkt->ol_flags = ol_flags;
> >  }
> > --
> > 1.8.3.1
> 


  reply	other threads:[~2020-10-13 15:39 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-10  3:10 yang_y_yi
2020-10-13  7:28 ` Hu, Jiayu
2020-10-13 15:39   ` Ananyev, Konstantin [this message]
2020-10-14  1:00     ` Hu, Jiayu
2020-10-14  2:56       ` yang_y_yi
2020-10-14 12:05         ` Ananyev, Konstantin
2020-10-15  5:14           ` Hu, Jiayu
2020-10-15 16:16             ` Ananyev, Konstantin
2020-10-16  0:53               ` Hu, Jiayu
2020-10-16  8:31                 ` Ananyev, Konstantin
2020-10-19  3:17                   ` Hu, Jiayu
2020-10-19  6:44                     ` yang_y_yi
2020-10-19  8:47                       ` Ananyev, Konstantin
2020-10-20  1:16                         ` yang_y_yi
2020-10-19  2:29                 ` yang_y_yi
2020-10-19  2:20               ` yang_y_yi

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