Subject: [PATCH 04/12 v2 RFC] skbuff: Push status and refcounts into sock_zerocopy_callback

From: Jonathan Lemon <[email-masked]>
Date: Mon, 21 Dec 2020 16:09:18 -0800

From: Jonathan Lemon <[email-masked]>

Before this change, the caller of sock_zerocopy_callback would
need to save the zerocopy status, decrement and check the refcount,
and then call the callback function - the callback was only invoked
when the refcount reached zero.

Now, the caller just passes the status into the callback function,
which saves the status and handles its own refcounts.

This makes the behavior of the sock_zerocopy_callback identical
to the tpacket and vhost callbacks.

Signed-off-by: Jonathan Lemon <[email-masked]>
---
 include/linux/skbuff.h |  3 ---
 net/core/skbuff.c      | 14 +++++++++++---
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index fb6dd6af0f82..c9d7de9d624d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1482,9 +1482,6 @@ static inline void skb_zcopy_clear(struct sk_buff *skb, bool zerocopy)
 	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);
 		}
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index ea32b3414ad6..73699dbdc4a1 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;
@@ -1241,11 +1241,19 @@ void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
 	consume_skb(skb);
 	sock_put(sk);
 }
+
+void sock_zerocopy_callback(struct ubuf_info *uarg, bool success)
+{
+	uarg->zerocopy = uarg->zerocopy & success;
+
+	if (refcount_dec_and_test(&uarg->refcnt))
+		__sock_zerocopy_callback(uarg);
+}
 EXPORT_SYMBOL_GPL(sock_zerocopy_callback);
 
 void sock_zerocopy_put(struct ubuf_info *uarg)
 {
-	if (uarg && refcount_dec_and_test(&uarg->refcnt))
+	if (uarg)
 		uarg->callback(uarg, uarg->zerocopy);
 }
 EXPORT_SYMBOL_GPL(sock_zerocopy_put);
-- 
2.24.1