skb_splice_bits(): get rid of callback

since pipe_lock is the outermost now, we don't need to drop/regain
socket locks around the call of splice_to_pipe() from skb_splice_bits(),
which kills the need to have a socket-specific callback; we can just
call splice_to_pipe() and be done with that.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

include/linux/skbuff.h

@@ -3021,15 +3021,9 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len);
 int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len);
 __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, u8 *to,
 			      int len, __wsum csum);
-ssize_t skb_socket_splice(struct sock *sk,
-			  struct pipe_inode_info *pipe,
-			  struct splice_pipe_desc *spd);
 int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
 		    struct pipe_inode_info *pipe, unsigned int len,
-		    unsigned int flags,
-		    ssize_t (*splice_cb)(struct sock *,
-					 struct pipe_inode_info *,
-					 struct splice_pipe_desc *));
+		    unsigned int flags);
 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
 unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
 int skb_zerocopy(struct sk_buff *to, struct sk_buff *from,

net/core/skbuff.c

@@ -1962,37 +1962,13 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
 	return false;
 }
 
-ssize_t skb_socket_splice(struct sock *sk,
-			  struct pipe_inode_info *pipe,
-			  struct splice_pipe_desc *spd)
-{
-	int ret;
-
-	/* Drop the socket lock, otherwise we have reverse
-	 * locking dependencies between sk_lock and i_mutex
-	 * here as compared to sendfile(). We enter here
-	 * with the socket lock held, and splice_to_pipe() will
-	 * grab the pipe inode lock. For sendfile() emulation,
-	 * we call into ->sendpage() with the i_mutex lock held
-	 * and networking will grab the socket lock.
-	 */
-	release_sock(sk);
-	ret = splice_to_pipe(pipe, spd);
-	lock_sock(sk);
-
-	return ret;
-}
-
 /*
  * Map data from the skb to a pipe. Should handle both the linear part,
  * the fragments, and the frag list.
  */
 int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
 		    struct pipe_inode_info *pipe, unsigned int tlen,
-		    unsigned int flags,
-		    ssize_t (*splice_cb)(struct sock *,
-					 struct pipe_inode_info *,
-					 struct splice_pipe_desc *))
+		    unsigned int flags)
 {
 	struct partial_page partial[MAX_SKB_FRAGS];
 	struct page *pages[MAX_SKB_FRAGS];
@@ -2009,7 +1985,7 @@ int skb_splice_bits(struct sk_buff *skb, struct sock *sk, unsigned int offset,
 	__skb_splice_bits(skb, pipe, &offset, &tlen, &spd, sk);
 
 	if (spd.nr_pages)
-		ret = splice_cb(sk, pipe, &spd);
+		ret = splice_to_pipe(pipe, &spd);
 
 	return ret;
 }

net/ipv4/tcp.c

@@ -688,8 +688,7 @@ static int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
 	int ret;
 
 	ret = skb_splice_bits(skb, skb->sk, offset, tss->pipe,
-			      min(rd_desc->count, len), tss->flags,
-			      skb_socket_splice);
+			      min(rd_desc->count, len), tss->flags);
 	if (ret > 0)
 		rd_desc->count -= ret;
 	return ret;

net/kcm/kcmsock.c

@@ -1462,19 +1462,6 @@ static int kcm_recvmsg(struct socket *sock, struct msghdr *msg,
 	return copied ? : err;
 }
 
-static ssize_t kcm_sock_splice(struct sock *sk,
-			       struct pipe_inode_info *pipe,
-			       struct splice_pipe_desc *spd)
-{
-	int ret;
-
-	release_sock(sk);
-	ret = splice_to_pipe(pipe, spd);
-	lock_sock(sk);
-
-	return ret;
-}
-
 static ssize_t kcm_splice_read(struct socket *sock, loff_t *ppos,
 			       struct pipe_inode_info *pipe, size_t len,
 			       unsigned int flags)
@@ -1504,8 +1491,7 @@ static ssize_t kcm_splice_read(struct socket *sock, loff_t *ppos,
 	if (len > rxm->full_len)
 		len = rxm->full_len;
 
-	copied = skb_splice_bits(skb, sk, rxm->offset, pipe, len, flags,
-				 kcm_sock_splice);
+	copied = skb_splice_bits(skb, sk, rxm->offset, pipe, len, flags);
 	if (copied < 0) {
 		err = copied;
 		goto err_out;

net/unix/af_unix.c

@@ -2475,28 +2475,13 @@ static int unix_stream_recvmsg(struct socket *sock, struct msghdr *msg,
 	return unix_stream_read_generic(&state);
 }
 
-static ssize_t skb_unix_socket_splice(struct sock *sk,
-				      struct pipe_inode_info *pipe,
-				      struct splice_pipe_desc *spd)
-{
-	int ret;
-	struct unix_sock *u = unix_sk(sk);
-
-	mutex_unlock(&u->iolock);
-	ret = splice_to_pipe(pipe, spd);
-	mutex_lock(&u->iolock);
-
-	return ret;
-}
-
 static int unix_stream_splice_actor(struct sk_buff *skb,
 				    int skip, int chunk,
 				    struct unix_stream_read_state *state)
 {
 	return skb_splice_bits(skb, state->socket->sk,
 			       UNIXCB(skb).consumed + skip,
-			       state->pipe, chunk, state->splice_flags,
-			       skb_unix_socket_splice);
+			       state->pipe, chunk, state->splice_flags);
 }
 
 static ssize_t unix_stream_splice_read(struct socket *sock,  loff_t *ppos,