From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Olivier Matz <olivier.matz@6wind.com>, "dev@dpdk.org" <dev@dpdk.org>
Cc: "andrew.rybchenko@oktetlabs.ru" <andrew.rybchenko@oktetlabs.ru>,
"mb@smartsharesystems.com" <mb@smartsharesystems.com>,
"alialnu@nvidia.com" <alialnu@nvidia.com>,
"ajitkhaparde@gmail.com" <ajitkhaparde@gmail.com>,
"stable@dpdk.org" <stable@dpdk.org>,
Ajit Khaparde <ajit.khaparde@broadcom.com>
Subject: Re: [dpdk-dev] [PATCH v3] mbuf: fix reset on mbuf free
Date: Mon, 11 Jan 2021 13:14:16 +0000 [thread overview]
Message-ID: <BYAPR11MB3301E703BC2129EFA798397F9AAB0@BYAPR11MB3301.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20210106133333.12528-1-olivier.matz@6wind.com>
> m->nb_seg must be reset on mbuf free whatever the value of m->next,
> because it can happen that m->nb_seg is != 1. For instance in this
> case:
>
> m1 = rte_pktmbuf_alloc(mp);
> rte_pktmbuf_append(m1, 500);
> m2 = rte_pktmbuf_alloc(mp);
> rte_pktmbuf_append(m2, 500);
> rte_pktmbuf_chain(m1, m2);
> m0 = rte_pktmbuf_alloc(mp);
> rte_pktmbuf_append(m0, 500);
> rte_pktmbuf_chain(m0, m1);
>
> As rte_pktmbuf_chain() does not reset nb_seg in the initial m1
> segment (this is not required), after this code the mbuf chain
> have 3 segments:
> - m0: next=m1, nb_seg=3
> - m1: next=m2, nb_seg=2
> - m2: next=NULL, nb_seg=1
>
> Then split this chain between m1 and m2, it would result in 2 packets:
> - first packet
> - m0: next=m1, nb_seg=2
> - m1: next=NULL, nb_seg=2
> - second packet
> - m2: next=NULL, nb_seg=1
>
> Freeing the first packet will not restore nb_seg=1 in the second
> segment. This is an issue because it is expected that mbufs stored
> in pool have their nb_seg field set to 1.
>
> Fixes: 8f094a9ac5d7 ("mbuf: set mbuf fields while in pool")
> Cc: stable@dpdk.org
>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> Acked-by: Morten Brørup <mb@smartsharesystems.com>
> Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
> ---
>
> v3
> * fix commit log again (thanks Morten for spotting it)
>
> v2
> * avoid write access if uneeded (suggested by Konstantin)
> * enhance comments in mbuf header file (suggested by Morten)
> * fix commit log
>
>
> lib/librte_mbuf/rte_mbuf.c | 4 ++--
> lib/librte_mbuf/rte_mbuf.h | 8 ++++----
> lib/librte_mbuf/rte_mbuf_core.h | 13 +++++++++++--
> 3 files changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
> index 7d09ee2939..5f77840557 100644
> --- a/lib/librte_mbuf/rte_mbuf.c
> +++ b/lib/librte_mbuf/rte_mbuf.c
> @@ -129,10 +129,10 @@ rte_pktmbuf_free_pinned_extmem(void *addr, void *opaque)
>
> rte_mbuf_ext_refcnt_set(m->shinfo, 1);
> m->ol_flags = EXT_ATTACHED_MBUF;
> - if (m->next != NULL) {
> + if (m->next != NULL)
> m->next = NULL;
> + if (m->nb_segs != 1)
> m->nb_segs = 1;
> - }
> rte_mbuf_raw_free(m);
> }
>
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index c4c9ebfaa0..8c1097ed76 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -1340,10 +1340,10 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
> return NULL;
> }
>
> - if (m->next != NULL) {
> + if (m->next != NULL)
> m->next = NULL;
> + if (m->nb_segs != 1)
> m->nb_segs = 1;
> - }
>
> return m;
>
> @@ -1357,10 +1357,10 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
> return NULL;
> }
>
> - if (m->next != NULL) {
> + if (m->next != NULL)
> m->next = NULL;
> + if (m->nb_segs != 1)
> m->nb_segs = 1;
> - }
> rte_mbuf_refcnt_set(m, 1);
>
> return m;
> diff --git a/lib/librte_mbuf/rte_mbuf_core.h b/lib/librte_mbuf/rte_mbuf_core.h
> index 567551deab..78a1fcc8ff 100644
> --- a/lib/librte_mbuf/rte_mbuf_core.h
> +++ b/lib/librte_mbuf/rte_mbuf_core.h
> @@ -495,7 +495,12 @@ struct rte_mbuf {
> * or non-atomic) is controlled by the RTE_MBUF_REFCNT_ATOMIC flag.
> */
> uint16_t refcnt;
> - uint16_t nb_segs; /**< Number of segments. */
> +
> + /**
> + * Number of segments. Only valid for the first segment of an mbuf
> + * chain.
> + */
> + uint16_t nb_segs;
>
> /** Input port (16 bits to support more than 256 virtual ports).
> * The event eth Tx adapter uses this field to specify the output port.
> @@ -591,7 +596,11 @@ struct rte_mbuf {
> /* second cache line - fields only used in slow path or on TX */
> RTE_MARKER cacheline1 __rte_cache_min_aligned;
>
> - struct rte_mbuf *next; /**< Next segment of scattered packet. */
> + /**
> + * Next segment of scattered packet. Must be NULL in the last segment or
> + * in case of non-segmented packet.
> + */
> + struct rte_mbuf *next;
>
> /* fields to support TX offloads */
> RTE_STD_C11
> --
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> 2.29.2
next prev parent reply other threads:[~2021-01-11 13:14 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-04 17:00 [dpdk-dev] [PATCH] " Olivier Matz
2020-11-05 0:15 ` Ananyev, Konstantin
2020-11-05 7:46 ` Olivier Matz
2020-11-05 8:26 ` Andrew Rybchenko
2020-11-05 9:10 ` Olivier Matz
2020-11-05 11:34 ` Ananyev, Konstantin
2020-11-05 12:31 ` Olivier Matz
2020-11-05 13:14 ` Ananyev, Konstantin
2020-11-05 13:24 ` Olivier Matz
2020-11-05 13:55 ` Ananyev, Konstantin
2020-11-05 16:30 ` Morten Brørup
2020-11-05 23:55 ` Ananyev, Konstantin
2020-11-06 7:52 ` Morten Brørup
2020-11-06 8:20 ` Olivier Matz
2020-11-06 8:50 ` Morten Brørup
2020-11-06 10:04 ` Olivier Matz
2020-11-06 10:07 ` Morten Brørup
2020-11-06 11:53 ` Ananyev, Konstantin
2020-11-06 12:23 ` Morten Brørup
2020-11-08 14:16 ` Andrew Rybchenko
2020-11-08 14:19 ` Ananyev, Konstantin
2020-11-10 16:26 ` Olivier Matz
2020-11-05 8:33 ` Morten Brørup
2020-11-05 9:03 ` Olivier Matz
2020-11-05 9:09 ` Andrew Rybchenko
2020-11-08 7:25 ` Ali Alnubani
2020-12-18 12:52 ` [dpdk-dev] [PATCH v2] " Olivier Matz
2020-12-18 13:18 ` Morten Brørup
2020-12-18 23:33 ` Ajit Khaparde
2021-01-06 13:33 ` [dpdk-dev] [PATCH v3] " Olivier Matz
2021-01-10 9:28 ` Ali Alnubani
2021-01-11 13:14 ` Ananyev, Konstantin [this message]
2021-01-13 13:27 ` [dpdk-dev] [PATCH v4] " Olivier Matz
2021-01-15 13:59 ` [dpdk-dev] [dpdk-stable] " David Marchand
2021-01-15 18:39 ` Ali Alnubani
2021-01-18 17:52 ` Ali Alnubani
2021-01-19 8:32 ` Olivier Matz
2021-01-19 8:53 ` Morten Brørup
2021-01-19 12:00 ` Ferruh Yigit
2021-01-19 12:27 ` Morten Brørup
2021-01-19 14:03 ` Ferruh Yigit
2021-01-19 14:21 ` Morten Brørup
2021-01-21 9:15 ` Ferruh Yigit
2021-01-19 14:04 ` Slava Ovsiienko
2021-07-24 8:47 ` Thomas Monjalon
2021-07-30 12:36 ` Olivier Matz
2021-07-30 14:35 ` Morten Brørup
2021-07-30 14:54 ` Thomas Monjalon
2021-07-30 15:14 ` Olivier Matz
2021-07-30 15:23 ` Morten Brørup
2021-08-04 13:29 ` [dpdk-dev] [PATCH] doc: add known issue with mbuf segment Thomas Monjalon
2021-08-04 14:25 ` Ajit Khaparde
2021-08-05 6:08 ` Morten Brørup
2021-08-06 14:21 ` Thomas Monjalon
2021-08-06 14:24 ` Morten Brørup
2021-09-28 8:28 ` [dpdk-dev] [dpdk-stable] [PATCH v4] mbuf: fix reset on mbuf free Thomas Monjalon
2021-09-28 9:00 ` Slava Ovsiienko
2021-09-28 9:25 ` Ananyev, Konstantin
2021-09-28 9:39 ` Morten Brørup
2021-09-29 8:03 ` Ali Alnubani
2021-09-29 21:39 ` Olivier Matz
2021-09-30 13:29 ` Ali Alnubani
2021-10-21 8:26 ` Thomas Monjalon
2021-01-21 9:19 ` Ferruh Yigit
2021-01-21 9:29 ` Morten Brørup
2021-01-21 16:35 ` [dpdk-dev] [dpdklab] " Lincoln Lavoie
2021-01-23 8:57 ` Morten Brørup
2021-01-25 17:00 ` Brandon Lo
2021-01-25 18:42 ` Ferruh Yigit
2021-06-15 13:56 ` [dpdk-dev] " Morten Brørup
2021-09-29 21:37 ` [dpdk-dev] [PATCH v5] " Olivier Matz
2021-09-30 13:27 ` Ali Alnubani
2021-10-21 9:18 ` David Marchand
2022-07-28 14:06 ` CI performance test results might be misleading Morten Brørup
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