xsk: Get rid of xdp_buff_xsk::xskb_list_node

Let's bring xdp_buff_xsk back to occupying 2 cachelines by removing
xskb_list_node - for the purpose of gathering the xskb frags
free_list_node can be used, head of the list (xsk_buff_pool::xskb_list)
stays as-is, just reuse the node ptr.

It is safe to do as a single xdp_buff_xsk can never reside in two
pool's lists simultaneously.

Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20241007122458.282590-2-maciej.fijalkowski@intel.com

4 files changed, 9 insertions, 11 deletions

diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 0a5dca2b2b3f..360bc1244c6a 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -126,8 +126,8 @@ static inline void xsk_buff_free(struct xdp_buff *xdp)
 	if (likely(!xdp_buff_has_frags(xdp)))
 		goto out;
 
-	list_for_each_entry_safe(pos, tmp, xskb_list, xskb_list_node) {
-		list_del(&pos->xskb_list_node);
+	list_for_each_entry_safe(pos, tmp, xskb_list, free_list_node) {
+		list_del(&pos->free_list_node);
 		xp_free(pos);
 	}
 
@@ -140,7 +140,7 @@ static inline void xsk_buff_add_frag(struct xdp_buff *xdp)
 {
 	struct xdp_buff_xsk *frag = container_of(xdp, struct xdp_buff_xsk, xdp);
 
-	list_add_tail(&frag->xskb_list_node, &frag->pool->xskb_list);
+	list_add_tail(&frag->free_list_node, &frag->pool->xskb_list);
 }
 
 static inline struct xdp_buff *xsk_buff_get_frag(struct xdp_buff *first)
@@ -150,9 +150,9 @@ static inline struct xdp_buff *xsk_buff_get_frag(struct xdp_buff *first)
 	struct xdp_buff_xsk *frag;
 
 	frag = list_first_entry_or_null(&xskb->pool->xskb_list,
-					struct xdp_buff_xsk, xskb_list_node);
+					struct xdp_buff_xsk, free_list_node);
 	if (frag) {
-		list_del(&frag->xskb_list_node);
+		list_del(&frag->free_list_node);
 		ret = &frag->xdp;
 	}
 
@@ -163,7 +163,7 @@ static inline void xsk_buff_del_tail(struct xdp_buff *tail)
 {
 	struct xdp_buff_xsk *xskb = container_of(tail, struct xdp_buff_xsk, xdp);
 
-	list_del(&xskb->xskb_list_node);
+	list_del(&xskb->free_list_node);
 }
 
 static inline struct xdp_buff *xsk_buff_get_tail(struct xdp_buff *first)
@@ -172,7 +172,7 @@ static inline struct xdp_buff *xsk_buff_get_tail(struct xdp_buff *first)
 	struct xdp_buff_xsk *frag;
 
 	frag = list_last_entry(&xskb->pool->xskb_list, struct xdp_buff_xsk,
-			       xskb_list_node);
+			       free_list_node);
 	return &frag->xdp;
 }
 
diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index bacb33f1e3e5..aa7f1d0b3a5e 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -30,7 +30,6 @@ struct xdp_buff_xsk {
 	struct xsk_buff_pool *pool;
 	u64 orig_addr;
 	struct list_head free_list_node;
-	struct list_head xskb_list_node;
 };
 
 #define XSK_CHECK_PRIV_TYPE(t) BUILD_BUG_ON(sizeof(t) > offsetofend(struct xdp_buff_xsk, cb))
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 1140b2a120ca..9c93064349a8 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -171,14 +171,14 @@ static int xsk_rcv_zc(struct xdp_sock *xs, struct xdp_buff *xdp, u32 len)
 		return 0;
 
 	xskb_list = &xskb->pool->xskb_list;
-	list_for_each_entry_safe(pos, tmp, xskb_list, xskb_list_node) {
+	list_for_each_entry_safe(pos, tmp, xskb_list, free_list_node) {
 		if (list_is_singular(xskb_list))
 			contd = 0;
 		len = pos->xdp.data_end - pos->xdp.data;
 		err = __xsk_rcv_zc(xs, pos, len, contd);
 		if (err)
 			goto err;
-		list_del(&pos->xskb_list_node);
+		list_del(&pos->free_list_node);
 	}
 
 	return 0;
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 521a2938e50a..e5368db7d18e 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -102,7 +102,6 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
 		xskb->pool = pool;
 		xskb->xdp.frame_sz = umem->chunk_size - umem->headroom;
 		INIT_LIST_HEAD(&xskb->free_list_node);
-		INIT_LIST_HEAD(&xskb->xskb_list_node);
 		if (pool->unaligned)
 			pool->free_heads[i] = xskb;
 		else