Re: [PATCH 15/15] net/dpaa: fix buffer free in slow path

[Ferruh Yigit <ferruh.yigit@amd.com>]

On 9/28/2022 6:25 AM, Gagandeep Singh wrote:
> Adding a check in slow path to free those buffers
> which are not external.
> 

Can you please explain what was the error before fix, what was happening 
when you try to free all mbufs?

Also it seems previous logic was different, with 'prev_seg' etc, can you 
explain what/why changed there?

> Fixes: 9124e65dd3eb ("net/dpaa: enable Tx queue taildrop")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Gagandeep Singh <g.singh@nxp.com>
> ---
>   drivers/net/dpaa/dpaa_rxtx.c | 23 ++++++++---------------
>   1 file changed, 8 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/net/dpaa/dpaa_rxtx.c b/drivers/net/dpaa/dpaa_rxtx.c
> index 4d285b4f38..ce4f3d6c85 100644
> --- a/drivers/net/dpaa/dpaa_rxtx.c
> +++ b/drivers/net/dpaa/dpaa_rxtx.c
> @@ -455,7 +455,7 @@ dpaa_free_mbuf(const struct qm_fd *fd)
>   	bp_info = DPAA_BPID_TO_POOL_INFO(fd->bpid);
>   	format = (fd->opaque & DPAA_FD_FORMAT_MASK) >> DPAA_FD_FORMAT_SHIFT;
>   	if (unlikely(format == qm_fd_sg)) {
> -		struct rte_mbuf *first_seg, *prev_seg, *cur_seg, *temp;
> +		struct rte_mbuf *first_seg, *cur_seg;
>   		struct qm_sg_entry *sgt, *sg_temp;
>   		void *vaddr, *sg_vaddr;
>   		int i = 0;
> @@ -469,32 +469,25 @@ dpaa_free_mbuf(const struct qm_fd *fd)
>   		sgt = vaddr + fd_offset;
>   		sg_temp = &sgt[i++];
>   		hw_sg_to_cpu(sg_temp);
> -		temp = (struct rte_mbuf *)
> -			((char *)vaddr - bp_info->meta_data_size);
>   		sg_vaddr = DPAA_MEMPOOL_PTOV(bp_info,
>   						qm_sg_entry_get64(sg_temp));
> -
>   		first_seg = (struct rte_mbuf *)((char *)sg_vaddr -
>   						bp_info->meta_data_size);
>   		first_seg->nb_segs = 1;
> -		prev_seg = first_seg;
>   		while (i < DPAA_SGT_MAX_ENTRIES) {
>   			sg_temp = &sgt[i++];
>   			hw_sg_to_cpu(sg_temp);
> -			sg_vaddr = DPAA_MEMPOOL_PTOV(bp_info,
> +			if (sg_temp->bpid != 0xFF) {
> +				bp_info = DPAA_BPID_TO_POOL_INFO(sg_temp->bpid);
> +				sg_vaddr = DPAA_MEMPOOL_PTOV(bp_info,
>   						qm_sg_entry_get64(sg_temp));
> -			cur_seg = (struct rte_mbuf *)((char *)sg_vaddr -
> +				cur_seg = (struct rte_mbuf *)((char *)sg_vaddr -
>   						      bp_info->meta_data_size);
> -			first_seg->nb_segs += 1;
> -			prev_seg->next = cur_seg;
> -			if (sg_temp->final) {
> -				cur_seg->next = NULL;
> -				break;
> +				rte_pktmbuf_free_seg(cur_seg);
>   			}
> -			prev_seg = cur_seg;
> +			if (sg_temp->final)
> +				break;
>   		}
> -
> -		rte_pktmbuf_free_seg(temp);
>   		rte_pktmbuf_free_seg(first_seg);
>   		return 0;
>   	}