[RFC PATCH v2 27/48] splice, net: Use sendmsg(MSG_SPLICE_PAGES) rather than ->sendpage()

David Howells
2023-03-29T14:19:55Z

Use sendmsg(MSG_SPLICE_PAGES) rather than ->sendpage() to splice data from
a pipe to a socket. This paves the way for passing in multiple pages at
once from a pipe and the handling of multipage folios.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
cc: netdev@vger.kernel.org
---
fs/splice.c | 42 +++++++++++++++++++++++-------------------
include/linux/fs.h | 2 --
include/linux/splice.h | 2 ++
net/socket.c | 26 ++------------------------
4 files changed, 27 insertions(+), 45 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index f46dd1fb367b..23ead122d631 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -32,6 +32,7 @@
#include <linux/uio.h>
#include <linux/security.h>
#include <linux/gfp.h>
+#include <linux/net.h>
#include <linux/socket.h>
#include <linux/sched/signal.h>

@@ -410,29 +411,32 @@ const struct pipe_buf_operations nosteal_pipe_buf_ops = {
};
EXPORT_SYMBOL(nosteal_pipe_buf_ops);

+#ifdef CONFIG_NET
/*
* Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
* using sendpage(). Return the number of bytes sent.
*/
-static int pipe_to_sendpage(struct pipe_inode_info *pipe,
- struct pipe_buffer *buf, struct splice_desc *sd)
+static int pipe_to_sendmsg(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf, struct splice_desc *sd)
{
- struct file *file = sd->u.file;
- loff_t pos = sd->pos;
- int more;
-
- if (!likely(file->f_op->sendpage))
- return -EINVAL;
+ struct socket *sock = sock_from_file(sd->u.file);
+ struct bio_vec bvec;
+ struct msghdr msg = {
+ .msg_flags = MSG_SPLICE_PAGES,
+ };

- more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
+ if (sd->flags & SPLICE_F_MORE)
+ msg.msg_flags |= MSG_MORE;

if (sd->len < sd->total_len &&
pipe_occupancy(pipe->head, pipe->tail) > 1)
- more |= MSG_SENDPAGE_NOTLAST;
+ msg.msg_flags |= MSG_MORE;

- return file->f_op->sendpage(file, buf->page, buf->offset,
- sd->len, &pos, more);
+ bvec_set_page(&bvec, buf->page, sd->len, buf->offset);
+ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, sd->len);
+ return sock_sendmsg(sock, &msg);
}
+#endif

static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
{
@@ -614,7 +618,7 @@ static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_des
* Description:
* This function does little more than loop over the pipe and call
* @actor to do the actual moving of a single struct pipe_buffer to
- * the desired destination. See pipe_to_file, pipe_to_sendpage, or
+ * the desired destination. See pipe_to_file, pipe_to_sendmsg, or
* pipe_to_user.
*
*/
@@ -795,8 +799,9 @@ iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,

EXPORT_SYMBOL(iter_file_splice_write);

+#ifdef CONFIG_NET
/**
- * generic_splice_sendpage - splice data from a pipe to a socket
+ * splice_to_socket - splice data from a pipe to a socket
* @pipe: pipe to splice from
* @out: socket to write to
* @ppos: position in @out
@@ -808,13 +813,12 @@ EXPORT_SYMBOL(iter_file_splice_write);
* is involved.
*
*/
-ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
- loff_t *ppos, size_t len, unsigned int flags)
+ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out,
+ loff_t *ppos, size_t len, unsigned int flags)
{
- return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
+ return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendmsg);
}
-
-EXPORT_SYMBOL(generic_splice_sendpage);
+#endif

static int warn_unsupported(struct file *file, const char *op)
{
diff --git a/include/linux/fs.h b/include/linux/fs.h
index c85916e9f7db..f3ccc243851e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2740,8 +2740,6 @@ extern ssize_t generic_file_splice_read(struct file *, loff_t *,
struct pipe_inode_info *, size_t, unsigned int);
extern ssize_t iter_file_splice_write(struct pipe_inode_info *,
struct file *, loff_t *, size_t, unsigned int);
-extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
- struct file *out, loff_t *, size_t len, unsigned int flags);
extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
loff_t *opos, size_t len, unsigned int flags);

diff --git a/include/linux/splice.h b/include/linux/splice.h
index 8f052c3dae95..e6153feda86c 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -87,6 +87,8 @@ extern long do_splice(struct file *in, loff_t *off_in,

extern long do_tee(struct file *in, struct file *out, size_t len,
unsigned int flags);
+extern ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out,
+ loff_t *ppos, size_t len, unsigned int flags);

/*
* for dynamic pipe sizing
diff --git a/net/socket.c b/net/socket.c
index dfb912bbed62..2cd5c2bcdde8 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -57,6 +57,7 @@
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/file.h>
+#include <linux/splice.h>
#include <linux/net.h>
#include <linux/interrupt.h>
#include <linux/thread_info.h>
@@ -126,8 +127,6 @@ static long compat_sock_ioctl(struct file *file,
unsigned int cmd, unsigned long arg);
#endif
static int sock_fasync(int fd, struct file *filp, int on);
-static ssize_t sock_sendpage(struct file *file, struct page *page,
- int offset, size_t size, loff_t *ppos, int more);
static ssize_t sock_splice_read(struct file *file, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags);
@@ -162,8 +161,7 @@ static const struct file_operations socket_file_ops = {
.mmap = sock_mmap,
.release = sock_close,
.fasync = sock_fasync,
- .sendpage = sock_sendpage,
- .splice_write = generic_splice_sendpage,
+ .splice_write = splice_to_socket,
.splice_read = sock_splice_read,
.show_fdinfo = sock_show_fdinfo,
};
@@ -1062,26 +1060,6 @@ int kernel_recvmsg(struct socket *sock, struct msghdr *msg,
}
EXPORT_SYMBOL(kernel_recvmsg);

-static ssize_t sock_sendpage(struct file *file, struct page *page,
- int offset, size_t size, loff_t *ppos, int more)
-{
- struct socket *sock;
- int flags;
- int ret;
-
- sock = file->private_data;
-
- flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;
- /* more is a combination of MSG_MORE and MSG_SENDPAGE_NOTLAST */
- flags |= more;
-
- ret = kernel_sendpage(sock, page, offset, size, flags);
-
- if (trace_sock_send_length_enabled())
- call_trace_sock_send_length(sock->sk, ret, 0);
- return ret;
-}
-
static ssize_t sock_splice_read(struct file *file, loff_t *ppos,
struct pipe_inode_info *pipe, size_t len,
unsigned int flags)