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From: Olivier Matz <olivier.matz@6wind.com>
To: dev@dpdk.org
Cc: andrew.rybchenko@oktetlabs.ru, konstantin.ananyev@intel.com,
	mb@smartsharesystems.com, stable@dpdk.org
Subject: [dpdk-stable] [PATCH v2] mbuf: fix reset on mbuf free
Date: Fri, 18 Dec 2020 13:52:37 +0100
Message-ID: <20201218125238.13074-1-olivier.matz@6wind.com> (raw)
In-Reply-To: <20201104170007.8026-1-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=3
    - m1: next=m2, 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>
---
 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
-- 
2.25.1


  parent reply	other threads:[~2020-12-18 12:52 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-04 17:00 [dpdk-stable] [PATCH] " Olivier Matz
2020-11-05  0:15 ` Ananyev, Konstantin
2020-11-05  7:46   ` Olivier Matz
2020-11-05  8:33     ` [dpdk-stable] [dpdk-dev] " 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 ` Olivier Matz [this message]
2020-12-18 13:18   ` [dpdk-stable] [dpdk-dev] [PATCH v2] " Morten Brørup
2020-12-18 23:33     ` Ajit Khaparde
2021-01-06 13:33 ` [dpdk-stable] [PATCH v3] " Olivier Matz
2021-01-10  9:28   ` Ali Alnubani
2021-01-11 13:14   ` Ananyev, Konstantin
2021-01-13 13:27 ` [dpdk-stable] [PATCH v4] " Olivier Matz
2021-01-15 13:59   ` 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               ` [dpdk-stable] [dpdk-dev] " 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           ` [dpdk-stable] " Slava Ovsiienko
2021-07-24  8:47             ` [dpdk-stable] [dpdk-dev] " 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
2021-01-21  9:19       ` [dpdk-stable] " Ferruh Yigit
2021-01-21  9:29         ` [dpdk-stable] [dpdk-dev] " Morten Brørup
2021-01-21 16:35           ` [dpdk-stable] [dpdklab] " Lincoln Lavoie
2021-01-23  8:57             ` [dpdk-stable] [dpdk-dev] [dpdklab] " Morten Brørup
2021-01-25 17:00               ` Brandon Lo
2021-01-25 18:42             ` [dpdk-stable] [dpdklab] RE: [dpdk-dev] " Ferruh Yigit
2021-06-15 13:56   ` [dpdk-stable] " Morten Brørup

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