[PATCH net-next v2] net: skbuff: optimization of net_zcopy_get() call in pskb_carve helpers

[PATCH net-next v2] net: skbuff: optimization of net_zcopy_get() call in pskb_carve helpers

[Yun Lu]

From: Yun Lu <luyun@kylinos.cn>

Commit 98d0912e9f84 ("net: skbuff: fix missing zerocopy reference in
pskb_carve helpers") introduced two calls of net_zcopy_get(skb_zcopy(skb)).
In fact, skb_zcopy() has already been executed once before. When calling
net_zcopy_get(), skb_zcopy() always returns skb_uarg(skb), which results
in adding some unnecessary instructions in skb_zcopy. So, change these
two calls to directly use skb_uarg(skb) instead of skb_zcopy.

In addition, also use net_zcopy_get() instead of refcount_inc() in
pskb_expand_head() for code consistency.

No functional change intended.

Signed-off-by: Yun Lu <luyun@kylinos.cn>

---
Changes in v2:
- Directly use skb_uarg(skb) instead of skb_zcopy.
  Thanks: Willem de Bruijn
- Links to v1: https://lore.kernel.org/all/20260706100229.13812-1-luyun_611@163.com/
---
 net/core/skbuff.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 18dabb4e9cfa..d798fbdc3da7 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2326,7 +2326,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 		if (skb_orphan_frags(skb, gfp_mask))
 			goto nofrags;
 		if (skb_zcopy(skb))
-			refcount_inc(&skb_uarg(skb)->refcnt);
+			net_zcopy_get(skb_uarg(skb));
 		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
 			skb_frag_ref(skb, i);
 
@@ -6842,7 +6842,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,
 			return -ENOMEM;
 		}
 		if (skb_zcopy(skb))
-			net_zcopy_get(skb_zcopy(skb));
+			net_zcopy_get(skb_uarg(skb));
 		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
 			skb_frag_ref(skb, i);
 		if (skb_has_frag_list(skb))
@@ -6992,7 +6992,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,
 		return -ENOMEM;
 	}
 	if (skb_zcopy(skb))
-		net_zcopy_get(skb_zcopy(skb));
+		net_zcopy_get(skb_uarg(skb));
 	skb_release_data(skb, SKB_CONSUMED);
 
 	skb->head = data;
-- 
2.43.0

Re: [PATCH net-next v2] net: skbuff: optimization of net_zcopy_get() call in pskb_carve helpers

[Willem de Bruijn]

Yun Lu wrote:
> From: Yun Lu <luyun@kylinos.cn>
> 
> Commit 98d0912e9f84 ("net: skbuff: fix missing zerocopy reference in
> pskb_carve helpers") introduced two calls of net_zcopy_get(skb_zcopy(skb)).
> In fact, skb_zcopy() has already been executed once before. When calling
> net_zcopy_get(), skb_zcopy() always returns skb_uarg(skb), which results
> in adding some unnecessary instructions in skb_zcopy. So, change these
> two calls to directly use skb_uarg(skb) instead of skb_zcopy.
> 
> In addition, also use net_zcopy_get() instead of refcount_inc() in
> pskb_expand_head() for code consistency.
> 
> No functional change intended.
> 
> Signed-off-by: Yun Lu <luyun@kylinos.cn>

Reviewed-by: Willem de Bruijn <willemb@google.com>