io_uring/net: move charging socket out of zc io_uring

Currently, io_uring's io_sg_from_iter() duplicates the part of
__zerocopy_sg_from_iter() charging pages to the socket. It'd be too easy
to miss while changing it in net/, the chunk is not the most
straightforward for outside users and full of internal implementation
details. io_uring is not a good place to keep it, deduplicate it by
moving out of the callback into __zerocopy_sg_from_iter().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/linux/skbuff.h

@@ -1703,6 +1703,9 @@ int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
 			    struct sk_buff *skb, struct iov_iter *from,
 			    size_t length);
 
+int zerocopy_fill_skb_from_iter(struct sk_buff *skb,
+				struct iov_iter *from, size_t length);
+
 static inline int skb_zerocopy_iter_dgram(struct sk_buff *skb,
 					  struct msghdr *msg, int len)
 {

include/linux/socket.h

@@ -76,7 +76,7 @@ struct msghdr {
 	__kernel_size_t	msg_controllen;	/* ancillary data buffer length */
 	struct kiocb	*msg_iocb;	/* ptr to iocb for async requests */
 	struct ubuf_info *msg_ubuf;
-	int (*sg_from_iter)(struct sock *sk, struct sk_buff *skb,
+	int (*sg_from_iter)(struct sk_buff *skb,
 			    struct iov_iter *from, size_t length);
 };
 

io_uring/net.c

@@ -1265,14 +1265,14 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	return io_sendmsg_prep_setup(req, req->opcode == IORING_OP_SENDMSG_ZC);
 }
 
-static int io_sg_from_iter_iovec(struct sock *sk, struct sk_buff *skb,
+static int io_sg_from_iter_iovec(struct sk_buff *skb,
 				 struct iov_iter *from, size_t length)
 {
 	skb_zcopy_downgrade_managed(skb);
-	return __zerocopy_sg_from_iter(NULL, sk, skb, from, length);
+	return zerocopy_fill_skb_from_iter(skb, from, length);
 }
 
-static int io_sg_from_iter(struct sock *sk, struct sk_buff *skb,
+static int io_sg_from_iter(struct sk_buff *skb,
 			   struct iov_iter *from, size_t length)
 {
 	struct skb_shared_info *shinfo = skb_shinfo(skb);
@@ -1285,7 +1285,7 @@ static int io_sg_from_iter(struct sock *sk, struct sk_buff *skb,
 	if (!frag)
 		shinfo->flags |= SKBFL_MANAGED_FRAG_REFS;
 	else if (unlikely(!skb_zcopy_managed(skb)))
-		return __zerocopy_sg_from_iter(NULL, sk, skb, from, length);
+		return zerocopy_fill_skb_from_iter(skb, from, length);
 
 	bi.bi_size = min(from->count, length);
 	bi.bi_bvec_done = from->iov_offset;
@@ -1312,14 +1312,6 @@ static int io_sg_from_iter(struct sock *sk, struct sk_buff *skb,
 	skb->data_len += copied;
 	skb->len += copied;
 	skb->truesize += truesize;
-
-	if (sk && sk->sk_type == SOCK_STREAM) {
-		sk_wmem_queued_add(sk, truesize);
-		if (!skb_zcopy_pure(skb))
-			sk_mem_charge(sk, truesize);
-	} else {
-		refcount_add(truesize, &skb->sk->sk_wmem_alloc);
-	}
 	return ret;
 }
 

net/core/datagram.c

@@ -610,8 +610,8 @@ int skb_copy_datagram_from_iter(struct sk_buff *skb, int offset,
 }
 EXPORT_SYMBOL(skb_copy_datagram_from_iter);
 
-static int zerocopy_fill_skb_from_iter(struct sk_buff *skb,
-					struct iov_iter *from, size_t length)
+int zerocopy_fill_skb_from_iter(struct sk_buff *skb,
+				struct iov_iter *from, size_t length)
 {
 	int frag = skb_shinfo(skb)->nr_frags;
 
@@ -687,11 +687,11 @@ int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
 	int ret;
 
 	if (msg && msg->msg_ubuf && msg->sg_from_iter)
-		return msg->sg_from_iter(sk, skb, from, length);
+		ret = msg->sg_from_iter(skb, from, length);
+	else
+		ret = zerocopy_fill_skb_from_iter(skb, from, length);
 
-	ret = zerocopy_fill_skb_from_iter(skb, from, length);
 	truesize = skb->truesize - orig_size;
-
 	if (sk && sk->sk_type == SOCK_STREAM) {
 		sk_wmem_queued_add(sk, truesize);
 		if (!skb_zcopy_pure(skb))