unix: Convert unix_stream_sendpage() to use MSG_SPLICE_PAGES

Convert unix_stream_sendpage() to use sendmsg() with MSG_SPLICE_PAGES
rather than directly splicing in the pages itself.

This allows ->sendpage() to be replaced by something that can handle
multiple multipage folios in a single transaction.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Kuniyuki Iwashima <kuniyu@amazon.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 976bc1c..115436c 100644 (file)
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1839,24 +1839,6 @@ static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock,
        }
 }
 
-static int maybe_init_creds(struct scm_cookie *scm,
-                           struct socket *socket,
-                           const struct sock *other)
-{
-       int err;
-       struct msghdr msg = { .msg_controllen = 0 };
-
-       err = scm_send(socket, &msg, scm, false);
-       if (err)
-               return err;
-
-       if (unix_passcred_enabled(socket, other)) {
-               scm->pid = get_pid(task_tgid(current));
-               current_uid_gid(&scm->creds.uid, &scm->creds.gid);
-       }
-       return err;
-}
-
 static bool unix_skb_scm_eq(struct sk_buff *skb,
                            struct scm_cookie *scm)
 {
@@ -2292,117 +2274,15 @@ out_err:
 static ssize_t unix_stream_sendpage(struct socket *socket, struct page *page,
                                    int offset, size_t size, int flags)
 {
-       int err;
-       bool send_sigpipe = false;
-       bool init_scm = true;
-       struct scm_cookie scm;
-       struct sock *other, *sk = socket->sk;
-       struct sk_buff *skb, *newskb = NULL, *tail = NULL;
-
-       if (flags & MSG_OOB)
-               return -EOPNOTSUPP;
+       struct bio_vec bvec;
+       struct msghdr msg = { .msg_flags = flags | MSG_SPLICE_PAGES };
 
-       other = unix_peer(sk);
-       if (!other || sk->sk_state != TCP_ESTABLISHED)
-               return -ENOTCONN;
-
-       if (false) {
-alloc_skb:
-               unix_state_unlock(other);
-               mutex_unlock(&unix_sk(other)->iolock);
-               newskb = sock_alloc_send_pskb(sk, 0, 0, flags & MSG_DONTWAIT,
-                                             &err, 0);
-               if (!newskb)
-                       goto err;
-       }
-
-       /* we must acquire iolock as we modify already present
-        * skbs in the sk_receive_queue and mess with skb->len
-        */
-       err = mutex_lock_interruptible(&unix_sk(other)->iolock);
-       if (err) {
-               err = flags & MSG_DONTWAIT ? -EAGAIN : -ERESTARTSYS;
-               goto err;
-       }
-
-       if (sk->sk_shutdown & SEND_SHUTDOWN) {
-               err = -EPIPE;
-               send_sigpipe = true;
-               goto err_unlock;
-       }
-
-       unix_state_lock(other);
+       if (flags & MSG_SENDPAGE_NOTLAST)
+               msg.msg_flags |= MSG_MORE;
 
-       if (sock_flag(other, SOCK_DEAD) ||
-           other->sk_shutdown & RCV_SHUTDOWN) {
-               err = -EPIPE;
-               send_sigpipe = true;
-               goto err_state_unlock;
-       }
-
-       if (init_scm) {
-               err = maybe_init_creds(&scm, socket, other);
-               if (err)
-                       goto err_state_unlock;
-               init_scm = false;
-       }
-
-       skb = skb_peek_tail(&other->sk_receive_queue);
-       if (tail && tail == skb) {
-               skb = newskb;
-       } else if (!skb || !unix_skb_scm_eq(skb, &scm)) {
-               if (newskb) {
-                       skb = newskb;
-               } else {
-                       tail = skb;
-                       goto alloc_skb;
-               }
-       } else if (newskb) {
-               /* this is fast path, we don't necessarily need to
-                * call to kfree_skb even though with newskb == NULL
-                * this - does no harm
-                */
-               consume_skb(newskb);
-               newskb = NULL;
-       }
-
-       if (skb_append_pagefrags(skb, page, offset, size, MAX_SKB_FRAGS)) {
-               tail = skb;
-               goto alloc_skb;
-       }
-
-       skb->len += size;
-       skb->data_len += size;
-       skb->truesize += size;
-       refcount_add(size, &sk->sk_wmem_alloc);
-
-       if (newskb) {
-               err = unix_scm_to_skb(&scm, skb, false);
-               if (err)
-                       goto err_state_unlock;
-               spin_lock(&other->sk_receive_queue.lock);
-               __skb_queue_tail(&other->sk_receive_queue, newskb);
-               spin_unlock(&other->sk_receive_queue.lock);
-       }
-
-       unix_state_unlock(other);
-       mutex_unlock(&unix_sk(other)->iolock);
-
-       other->sk_data_ready(other);
-       scm_destroy(&scm);
-       return size;
-
-err_state_unlock:
-       unix_state_unlock(other);
-err_unlock:
-       mutex_unlock(&unix_sk(other)->iolock);
-err:
-       kfree_skb(newskb);
-       if (send_sigpipe && !(flags & MSG_NOSIGNAL))
-               send_sig(SIGPIPE, current, 0);
-       if (!init_scm)
-               scm_destroy(&scm);
-       return err;
+       bvec_set_page(&bvec, page, size, offset);
+       iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
+       return unix_stream_sendmsg(socket, &msg, size);
 }
 
 static int unix_seqpacket_sendmsg(struct socket *sock, struct msghdr *msg,