Subject: [PATCH 3/9 v1 RFC] skbuff: replace sock_zerocopy_put() with skb_zcopy_put()

From: Jonathan Lemon <[email-masked]>
Date: Fri, 18 Dec 2020 12:16:27 -0800

From: Jonathan Lemon <[email-masked]>

In preparation for further work, the zcopy* routines will
become basic building blocks, while the zerocopy* ones will
be specific for the existing zerocopy implementation.

All uargs should have a callback function, (unless nouarg
is set), so push all special case logic handling down into
the callbacks.  This slightly pessimizes the refcounted cases,
but makes the skb_zcopy_*() routines clearer.

Signed-off-by: Jonathan Lemon <[email-masked]>
---
 include/linux/skbuff.h | 19 +++++++++----------
 net/core/skbuff.c      | 21 +++++++++------------
 net/ipv4/tcp.c         |  2 +-
 3 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index fb6dd6af0f82..df98d61e8c51 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -499,7 +499,6 @@ static inline void sock_zerocopy_get(struct ubuf_info *uarg)
 	refcount_inc(&uarg->refcnt);
 }
 
-void sock_zerocopy_put(struct ubuf_info *uarg);
 void sock_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref);
 
 void sock_zerocopy_callback(struct ubuf_info *uarg, bool success);
@@ -1474,20 +1473,20 @@ static inline void *skb_zcopy_get_nouarg(struct sk_buff *skb)
 	return (void *)((uintptr_t) skb_shinfo(skb)->destructor_arg & ~0x1UL);
 }
 
+static inline void skb_zcopy_put(struct ubuf_info *uarg)
+{
+	if (uarg)
+		uarg->callback(uarg, true);
+}
+
 /* Release a reference on a zerocopy structure */
-static inline void skb_zcopy_clear(struct sk_buff *skb, bool zerocopy)
+static inline void skb_zcopy_clear(struct sk_buff *skb, bool succsss)
 {
 	struct ubuf_info *uarg = skb_zcopy(skb);
 
 	if (uarg) {
-		if (skb_zcopy_is_nouarg(skb)) {
-			/* no notification callback */
-		} else if (uarg->callback == sock_zerocopy_callback) {
-			uarg->zerocopy = uarg->zerocopy && zerocopy;
-			sock_zerocopy_put(uarg);
-		} else {
-			uarg->callback(uarg, zerocopy);
-		}
+		if (!skb_zcopy_is_nouarg(skb))
+			uarg->callback(uarg, succsss);
 
 		skb_shinfo(skb)->zc_flags &= ~SKBZC_FRAGMENTS;
 	}
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 327ee8938f78..984760dd670b 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1194,7 +1194,7 @@ static bool skb_zerocopy_notify_extend(struct sk_buff *skb, u32 lo, u16 len)
 	return true;
 }
 
-void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
+static void __sock_zerocopy_callback(struct ubuf_info *uarg)
 {
 	struct sk_buff *tail, *skb = skb_from_uarg(uarg);
 	struct sock_exterr_skb *serr;
@@ -1222,7 +1222,7 @@ void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
 	serr->ee.ee_origin = SO_EE_ORIGIN_ZEROCOPY;
 	serr->ee.ee_data = hi;
 	serr->ee.ee_info = lo;
-	if (!success)
+	if (!uarg->zerocopy)
 		serr->ee.ee_code |= SO_EE_CODE_ZEROCOPY_COPIED;
 
 	q = &sk->sk_error_queue;
@@ -1241,18 +1241,15 @@ void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
 	consume_skb(skb);
 	sock_put(sk);
 }
-EXPORT_SYMBOL_GPL(sock_zerocopy_callback);
 
-void sock_zerocopy_put(struct ubuf_info *uarg)
+void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
 {
-	if (uarg && refcount_dec_and_test(&uarg->refcnt)) {
-		if (uarg->callback)
-			uarg->callback(uarg, uarg->zerocopy);
-		else
-			consume_skb(skb_from_uarg(uarg));
-	}
+	uarg->zerocopy = uarg->zerocopy & success;
+
+	if (refcount_dec_and_test(&uarg->refcnt))
+		__sock_zerocopy_callback(uarg);
 }
-EXPORT_SYMBOL_GPL(sock_zerocopy_put);
+EXPORT_SYMBOL_GPL(sock_zerocopy_callback);
 
 void sock_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref)
 {
@@ -1263,7 +1260,7 @@ void sock_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref)
 		uarg->len--;
 
 		if (have_uref)
-			sock_zerocopy_put(uarg);
+			skb_zcopy_put(uarg);
 	}
 }
 EXPORT_SYMBOL_GPL(sock_zerocopy_put_abort);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index fea9bae370e4..5c38080df13f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1429,7 +1429,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 		tcp_push(sk, flags, mss_now, tp->nonagle, size_goal);
 	}
 out_nopush:
-	sock_zerocopy_put(uarg);
+	skb_zcopy_put(uarg);
 	return copied + copied_syn;
 
 do_error:
-- 
2.24.1