[dpdk-dev] [PATCH] net/enic: decrement Tx mbuf reference count before recycling

[John Daley]

In the Tx cleanup function, the reference count in mbufs to be
returned to the pool should to be decremented before they are
returned. Decrementing is not done by rte_mempool_put_bulk()
so it must be done separately using __rte_pktmbuf_prefree_seg().
If decrementing does not result in a 0 reference count the mbuf
is not returned to the pool and whatever has the last reference
is responsible for freeing.

Fixes: 36935afbc53c ("net/enic: refactor Tx mbuf recycling")
Reviewed-by: Nelson Escobar <neescoba at cisco.com>
Signed-off-by: John Daley <johndale at cisco.com>
---
Since reference counts are set to 0 when mbufs are reallocated from the
pool, and sending packets with reference count not equal to 1 is probably
an application error, this patch may not be critical. But a debug ASSERT
caught it and it would be nice to have it fixed in 16.07.

 drivers/net/enic/enic_rxtx.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/enic/enic_rxtx.c b/drivers/net/enic/enic_rxtx.c
index 5ac1d69..96be478 100644
--- a/drivers/net/enic/enic_rxtx.c
+++ b/drivers/net/enic/enic_rxtx.c
@@ -398,7 +398,14 @@ static inline void enic_free_wq_bufs(struct vnic_wq *wq, u16 completed_index)
 	pool = ((struct rte_mbuf *)buf->mb)->pool;
 	for (i = 0; i < nb_to_free; i++) {
 		buf = &wq->bufs[tail_idx];
-		m = (struct rte_mbuf *)(buf->mb);
+		m = __rte_pktmbuf_prefree_seg((struct rte_mbuf *)(buf->mb));
+		buf->mb = NULL;
+
+		if (unlikely(m == NULL)) {
+			tail_idx = enic_ring_incr(desc_count, tail_idx);
+			continue;
+		}
+
 		if (likely(m->pool == pool)) {
 			ENIC_ASSERT(nb_free < ENIC_MAX_WQ_DESCS);
 			free[nb_free++] = m;
@@ -409,7 +416,6 @@ static inline void enic_free_wq_bufs(struct vnic_wq *wq, u16 completed_index)
 			pool = m->pool;
 		}
 		tail_idx = enic_ring_incr(desc_count, tail_idx);
-		buf->mb = NULL;
 	}
 
 	rte_mempool_put_bulk(pool, (void **)free, nb_free);
-- 
2.7.0