[RFC 1/6] net: extend ubuf_info callback to ops structure

[Pavel Begunkov <asml.silence@gmail.com>]

We'll need to associate additional callbacks with ubuf_info, introduce
a structure holding ubuf_info callbacks. Apart from a more smarter
io_uring notification management introduced in next patches, it can be
used to generalise msg_zerocopy_put_abort() and also store
->sg_from_iter, which is currently passed in struct msghdr.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 drivers/net/tap.c      |  2 +-
 drivers/net/tun.c      |  2 +-
 drivers/vhost/net.c    |  8 ++++++--
 include/linux/skbuff.h | 19 +++++++++++--------
 io_uring/notif.c       |  8 ++++++--
 net/core/skbuff.c      | 17 +++++++++++------
 6 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 9f0495e8df4d..bfdd3875fe86 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -754,7 +754,7 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
 		skb_zcopy_init(skb, msg_control);
 	} else if (msg_control) {
 		struct ubuf_info *uarg = msg_control;
-		uarg->callback(NULL, uarg, false);
+		uarg->ops->complete(NULL, uarg, false);
 	}
 
 	dev_queue_xmit(skb);
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 0b3f21cba552..b7401d990680 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1906,7 +1906,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
 		skb_zcopy_init(skb, msg_control);
 	} else if (msg_control) {
 		struct ubuf_info *uarg = msg_control;
-		uarg->callback(NULL, uarg, false);
+		uarg->ops->complete(NULL, uarg, false);
 	}
 
 	skb_reset_network_header(skb);
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index c64ded183f8d..f16279351db5 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -380,7 +380,7 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net,
 	}
 }
 
-static void vhost_zerocopy_callback(struct sk_buff *skb,
+static void vhost_zerocopy_complete(struct sk_buff *skb,
 				    struct ubuf_info *ubuf_base, bool success)
 {
 	struct ubuf_info_msgzc *ubuf = uarg_to_msgzc(ubuf_base);
@@ -408,6 +408,10 @@ static void vhost_zerocopy_callback(struct sk_buff *skb,
 	rcu_read_unlock_bh();
 }
 
+static const struct ubuf_info_ops vhost_ubuf_ops = {
+	.complete = vhost_zerocopy_complete,
+};
+
 static inline unsigned long busy_clock(void)
 {
 	return local_clock() >> 10;
@@ -879,7 +883,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
 			vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
 			ubuf->ctx = nvq->ubufs;
 			ubuf->desc = nvq->upend_idx;
-			ubuf->ubuf.callback = vhost_zerocopy_callback;
+			ubuf->ubuf.ops = &vhost_ubuf_ops;
 			ubuf->ubuf.flags = SKBFL_ZEROCOPY_FRAG;
 			refcount_set(&ubuf->ubuf.refcnt, 1);
 			msg.msg_control = &ctl;
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 9d24aec064e8..a110e97e074a 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -527,6 +527,11 @@ enum {
 #define SKBFL_ALL_ZEROCOPY	(SKBFL_ZEROCOPY_FRAG | SKBFL_PURE_ZEROCOPY | \
 				 SKBFL_DONT_ORPHAN | SKBFL_MANAGED_FRAG_REFS)
 
+struct ubuf_info_ops {
+	void (*complete)(struct sk_buff *, struct ubuf_info *,
+			 bool zerocopy_success);
+};
+
 /*
  * The callback notifies userspace to release buffers when skb DMA is done in
  * lower device, the skb last reference should be 0 when calling this.
@@ -536,8 +541,7 @@ enum {
  * The desc field is used to track userspace buffer index.
  */
 struct ubuf_info {
-	void (*callback)(struct sk_buff *, struct ubuf_info *,
-			 bool zerocopy_success);
+	const struct ubuf_info_ops *ops;
 	refcount_t refcnt;
 	u8 flags;
 };
@@ -1662,14 +1666,13 @@ static inline void skb_set_end_offset(struct sk_buff *skb, unsigned int offset)
 }
 #endif
 
+extern const struct ubuf_info_ops msg_zerocopy_ubuf_ops;
+
 struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
 				       struct ubuf_info *uarg);
 
 void msg_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref);
 
-void msg_zerocopy_callback(struct sk_buff *skb, struct ubuf_info *uarg,
-			   bool success);
-
 int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
 			    struct sk_buff *skb, struct iov_iter *from,
 			    size_t length);
@@ -1757,13 +1760,13 @@ static inline void *skb_zcopy_get_nouarg(struct sk_buff *skb)
 static inline void net_zcopy_put(struct ubuf_info *uarg)
 {
 	if (uarg)
-		uarg->callback(NULL, uarg, true);
+		uarg->ops->complete(NULL, uarg, true);
 }
 
 static inline void net_zcopy_put_abort(struct ubuf_info *uarg, bool have_uref)
 {
 	if (uarg) {
-		if (uarg->callback == msg_zerocopy_callback)
+		if (uarg->ops == &msg_zerocopy_ubuf_ops)
 			msg_zerocopy_put_abort(uarg, have_uref);
 		else if (have_uref)
 			net_zcopy_put(uarg);
@@ -1777,7 +1780,7 @@ static inline void skb_zcopy_clear(struct sk_buff *skb, bool zerocopy_success)
 
 	if (uarg) {
 		if (!skb_zcopy_is_nouarg(skb))
-			uarg->callback(skb, uarg, zerocopy_success);
+			uarg->ops->complete(skb, uarg, zerocopy_success);
 
 		skb_shinfo(skb)->flags &= ~SKBFL_ALL_ZEROCOPY;
 	}
diff --git a/io_uring/notif.c b/io_uring/notif.c
index b561bd763435..7caaebf94312 100644
--- a/io_uring/notif.c
+++ b/io_uring/notif.c
@@ -24,7 +24,7 @@ void io_notif_tw_complete(struct io_kiocb *notif, struct io_tw_state *ts)
 	io_req_task_complete(notif, ts);
 }
 
-static void io_tx_ubuf_callback(struct sk_buff *skb, struct ubuf_info *uarg,
+static void io_tx_ubuf_complete(struct sk_buff *skb, struct ubuf_info *uarg,
 				bool success)
 {
 	struct io_notif_data *nd = container_of(uarg, struct io_notif_data, uarg);
@@ -43,6 +43,10 @@ static void io_tx_ubuf_callback(struct sk_buff *skb, struct ubuf_info *uarg,
 	}
 }
 
+static const struct ubuf_info_ops io_ubuf_ops = {
+	.complete = io_tx_ubuf_complete,
+};
+
 struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
 	__must_hold(&ctx->uring_lock)
 {
@@ -62,7 +66,7 @@ struct io_kiocb *io_alloc_notif(struct io_ring_ctx *ctx)
 	nd->zc_report = false;
 	nd->account_pages = 0;
 	nd->uarg.flags = IO_NOTIF_UBUF_FLAGS;
-	nd->uarg.callback = io_tx_ubuf_callback;
+	nd->uarg.ops = &io_ubuf_ops;
 	refcount_set(&nd->uarg.refcnt, 1);
 	return notif;
 }
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b99127712e67..749abab23a67 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1708,7 +1708,7 @@ static struct ubuf_info *msg_zerocopy_alloc(struct sock *sk, size_t size)
 		return NULL;
 	}
 
-	uarg->ubuf.callback = msg_zerocopy_callback;
+	uarg->ubuf.ops = &msg_zerocopy_ubuf_ops;
 	uarg->id = ((u32)atomic_inc_return(&sk->sk_zckey)) - 1;
 	uarg->len = 1;
 	uarg->bytelen = size;
@@ -1734,7 +1734,7 @@ struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
 		u32 bytelen, next;
 
 		/* there might be non MSG_ZEROCOPY users */
-		if (uarg->callback != msg_zerocopy_callback)
+		if (uarg->ops != &msg_zerocopy_ubuf_ops)
 			return NULL;
 
 		/* realloc only when socket is locked (TCP, UDP cork),
@@ -1845,8 +1845,8 @@ static void __msg_zerocopy_callback(struct ubuf_info_msgzc *uarg)
 	sock_put(sk);
 }
 
-void msg_zerocopy_callback(struct sk_buff *skb, struct ubuf_info *uarg,
-			   bool success)
+static void msg_zerocopy_complete(struct sk_buff *skb, struct ubuf_info *uarg,
+				  bool success)
 {
 	struct ubuf_info_msgzc *uarg_zc = uarg_to_msgzc(uarg);
 
@@ -1855,7 +1855,7 @@ void msg_zerocopy_callback(struct sk_buff *skb, struct ubuf_info *uarg,
 	if (refcount_dec_and_test(&uarg->refcnt))
 		__msg_zerocopy_callback(uarg_zc);
 }
-EXPORT_SYMBOL_GPL(msg_zerocopy_callback);
+
 
 void msg_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref)
 {
@@ -1865,10 +1865,15 @@ void msg_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref)
 	uarg_to_msgzc(uarg)->len--;
 
 	if (have_uref)
-		msg_zerocopy_callback(NULL, uarg, true);
+		msg_zerocopy_complete(NULL, uarg, true);
 }
 EXPORT_SYMBOL_GPL(msg_zerocopy_put_abort);
 
+const struct ubuf_info_ops msg_zerocopy_ubuf_ops = {
+	.complete = msg_zerocopy_complete,
+};
+EXPORT_SYMBOL_GPL(msg_zerocopy_ubuf_ops);
+
 int skb_zerocopy_iter_stream(struct sock *sk, struct sk_buff *skb,
 			     struct msghdr *msg, int len,
 			     struct ubuf_info *uarg)
-- 
2.44.0