On Fri, Apr 15, 2022 at 02:29:43PM +0200, Jakob Koschel wrote:
> In preparation to limit the scope of a list iterator to the list
> traversal loop, use a dedicated pointer pointing to the location
> where the element should be inserted [1].
>
> Before, the code implicitly used the head when no element was found
> when using &new->list. The new 'pos' variable is set to the list head
> by default and overwritten if the list exits early, marking the
> insertion point for list_add().
>
> Link:
> https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=ehreask5sqxpwr9y7k9sa6cwx...@mail.gmail.com/
> [1]
> Signed-off-by: Jakob Koschel <jakobkosc...@gmail.com>
> ---
> drivers/net/ethernet/sfc/rx_common.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/sfc/rx_common.c
> b/drivers/net/ethernet/sfc/rx_common.c
> index 1b22c7be0088..716847ba7038 100644
> --- a/drivers/net/ethernet/sfc/rx_common.c
> +++ b/drivers/net/ethernet/sfc/rx_common.c
> @@ -556,6 +556,7 @@ efx_rx_packet_gro(struct efx_channel *channel, struct
> efx_rx_buffer *rx_buf,
> struct efx_rss_context *efx_alloc_rss_context_entry(struct efx_nic *efx)
> {
> struct list_head *head = &efx->rss_context.list;
> + struct list_head *pos = head;
This violates the reverse Xmas list policy. This definition should be
1 line further down.
Martin
> struct efx_rss_context *ctx, *new;
> u32 id = 1; /* Don't use zero, that refers to the master RSS context */
>
> @@ -563,8 +564,10 @@ struct efx_rss_context
> *efx_alloc_rss_context_entry(struct efx_nic *efx)
>
> /* Search for first gap in the numbering */
> list_for_each_entry(ctx, head, list) {
> - if (ctx->user_id != id)
> + if (ctx->user_id != id) {
> + pos = &ctx->list;
> break;
> + }
> id++;
> /* Check for wrap. If this happens, we have nearly 2^32
> * allocated RSS contexts, which seems unlikely.
> @@ -582,7 +585,7 @@ struct efx_rss_context
> *efx_alloc_rss_context_entry(struct efx_nic *efx)
>
> /* Insert the new entry into the gap */
> new->user_id = id;
> - list_add_tail(&new->list, &ctx->list);
> + list_add_tail(&new->list, pos);
> return new;
> }
>
> --
> 2.25.1
