[RFC net-next v3 04/29] skbuff: carry external ubuf_info in msghdr

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

Make possible for network in-kernel callers like io_uring to pass in a
custom ubuf_info by setting it in a new field of struct msghdr.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c          | 4 ++++
 include/linux/socket.h | 7 +++++++
 net/compat.c           | 2 ++
 net/socket.c           | 6 ++++++
 4 files changed, 19 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8e75539fdc1d..6a57a5ae18fb 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6230,6 +6230,8 @@ static int io_send(struct io_kiocb *req, unsigned int issue_flags)
 	msg.msg_control = NULL;
 	msg.msg_controllen = 0;
 	msg.msg_namelen = 0;
+	msg.msg_ubuf = NULL;
+	msg.msg_managed_data = false;
 
 	flags = sr->msg_flags;
 	if (issue_flags & IO_URING_F_NONBLOCK)
@@ -6500,6 +6502,8 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 	msg.msg_flags = 0;
 	msg.msg_controllen = 0;
 	msg.msg_iocb = NULL;
+	msg.msg_ubuf = NULL;
+	msg.msg_managed_data = false;
 
 	flags = sr->msg_flags;
 	if (force_nonblock)
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 17311ad9f9af..ba84ee614d5a 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -66,9 +66,16 @@ struct msghdr {
 	};
 	bool		msg_control_is_user : 1;
 	bool		msg_get_inq : 1;/* return INQ after receive */
+	/*
+	 * The data pages are pinned and won't be released before ->msg_ubuf
+	 * is released. ->msg_iter should point to a bvec and ->msg_ubuf has
+	 * to be non-NULL.
+	 */
+	bool		msg_managed_data : 1;
 	unsigned int	msg_flags;	/* flags on received message */
 	__kernel_size_t	msg_controllen;	/* ancillary data buffer length */
 	struct kiocb	*msg_iocb;	/* ptr to iocb for async requests */
+	struct ubuf_info *msg_ubuf;
 };
 
 struct user_msghdr {
diff --git a/net/compat.c b/net/compat.c
index 210fc3b4d0d8..435846fa85e0 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -80,6 +80,8 @@ int __get_compat_msghdr(struct msghdr *kmsg,
 		return -EMSGSIZE;
 
 	kmsg->msg_iocb = NULL;
+	kmsg->msg_ubuf = NULL;
+	kmsg->msg_managed_data = false;
 	*ptr = msg.msg_iov;
 	*len = msg.msg_iovlen;
 	return 0;
diff --git a/net/socket.c b/net/socket.c
index 2bc8773d9dc5..0963a02b1472 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2106,6 +2106,8 @@ int __sys_sendto(int fd, void __user *buff, size_t len, unsigned int flags,
 	msg.msg_control = NULL;
 	msg.msg_controllen = 0;
 	msg.msg_namelen = 0;
+	msg.msg_ubuf = NULL;
+	msg.msg_managed_data = false;
 	if (addr) {
 		err = move_addr_to_kernel(addr, addr_len, &address);
 		if (err < 0)
@@ -2171,6 +2173,8 @@ int __sys_recvfrom(int fd, void __user *ubuf, size_t size, unsigned int flags,
 	msg.msg_namelen = 0;
 	msg.msg_iocb = NULL;
 	msg.msg_flags = 0;
+	msg.msg_ubuf = NULL;
+	msg.msg_managed_data = false;
 	if (sock->file->f_flags & O_NONBLOCK)
 		flags |= MSG_DONTWAIT;
 	err = sock_recvmsg(sock, &msg, flags);
@@ -2409,6 +2413,8 @@ int __copy_msghdr_from_user(struct msghdr *kmsg,
 		return -EMSGSIZE;
 
 	kmsg->msg_iocb = NULL;
+	kmsg->msg_ubuf = NULL;
+	kmsg->msg_managed_data = false;
 	*uiov = msg.msg_iov;
 	*nsegs = msg.msg_iovlen;
 	return 0;
-- 
2.36.1