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splice, net: Use sendmsg(MSG_SPLICE_PAGES) rather than ->sendpage()

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Replace generic_splice_sendpage() + splice_from_pipe + pipe_to_sendpage()
with a net-specific handler, splice_to_socket(), that calls sendmsg() with
MSG_SPLICE_PAGES set instead of calling ->sendpage().

MSG_MORE is used to indicate if the sendmsg() is expected to be followed
with more data.

This allows multiple pipe-buffer pages to be passed in a single call in a
BVEC iterator, allowing the processing to be pushed down to a loop in the
protocol driver.  This helps pave the way for passing multipage folios down
too.

Protocols that haven't been converted to handle MSG_SPLICE_PAGES yet should
just ignore it and do a normal sendmsg() for now - although that may be a
bit slower as it may copy everything.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
David Howells 2023-06-07 19:19:09 +01:00 committed by Jakub Kicinski
parent 81840b3b91
commit 2dc334f1a6
4 changed files with 131 additions and 57 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

158
fs/splice.c
View file

@ -33,6 +33,7 @@
#include <linux/fsnotify.h>
#include <linux/security.h>
#include <linux/gfp.h>
#include <linux/net.h>
#include <linux/socket.h>
#include <linux/sched/signal.h>
@ -448,30 +449,6 @@ const struct pipe_buf_operations nosteal_pipe_buf_ops = {
};
EXPORT_SYMBOL(nosteal_pipe_buf_ops);
/*
* 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)
{
struct file *file = sd->u.file;
loff_t pos = sd->pos;
int more;
if (!likely(file->f_op->sendpage))
return -EINVAL;
more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
if (sd->len < sd->total_len &&
pipe_occupancy(pipe->head, pipe->tail) > 1)
more |= MSG_SENDPAGE_NOTLAST;
return file->f_op->sendpage(file, buf->page, buf->offset,
sd->len, &pos, more);
}
static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
{
smp_mb();
@ -652,7 +629,7 @@ 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.
*
*/
@ -833,8 +810,9 @@ 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
@ -846,13 +824,131 @@ 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);
}
struct socket *sock = sock_from_file(out);
struct bio_vec bvec[16];
struct msghdr msg = {};
ssize_t ret = 0;
size_t spliced = 0;
bool need_wakeup = false;
EXPORT_SYMBOL(generic_splice_sendpage);
pipe_lock(pipe);
while (len > 0) {
unsigned int head, tail, mask, bc = 0;
size_t remain = len;
/*
* Check for signal early to make process killable when there
* are always buffers available
*/
ret = -ERESTARTSYS;
if (signal_pending(current))
break;
while (pipe_empty(pipe->head, pipe->tail)) {
ret = 0;
if (!pipe->writers)
goto out;
if (spliced)
goto out;
ret = -EAGAIN;
if (flags & SPLICE_F_NONBLOCK)
goto out;
ret = -ERESTARTSYS;
if (signal_pending(current))
goto out;
if (need_wakeup) {
wakeup_pipe_writers(pipe);
need_wakeup = false;
}
pipe_wait_readable(pipe);
}
head = pipe->head;
tail = pipe->tail;
mask = pipe->ring_size - 1;
while (!pipe_empty(head, tail)) {
struct pipe_buffer *buf = &pipe->bufs[tail & mask];
size_t seg;
if (!buf->len) {
tail++;
continue;
}
seg = min_t(size_t, remain, buf->len);
seg = min_t(size_t, seg, PAGE_SIZE);
ret = pipe_buf_confirm(pipe, buf);
if (unlikely(ret)) {
if (ret == -ENODATA)
ret = 0;
break;
}
bvec_set_page(&bvec[bc++], buf->page, seg, buf->offset);
remain -= seg;
if (seg >= buf->len)
tail++;
if (bc >= ARRAY_SIZE(bvec))
break;
}
if (!bc)
break;
msg.msg_flags = MSG_SPLICE_PAGES;
if (flags & SPLICE_F_MORE)
msg.msg_flags |= MSG_MORE;
if (remain && pipe_occupancy(pipe->head, tail) > 0)
msg.msg_flags |= MSG_MORE;
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, bvec, bc,
len - remain);
ret = sock_sendmsg(sock, &msg);
if (ret <= 0)
break;
spliced += ret;
len -= ret;
tail = pipe->tail;
while (ret > 0) {
struct pipe_buffer *buf = &pipe->bufs[tail & mask];
size_t seg = min_t(size_t, ret, buf->len);
buf->offset += seg;
buf->len -= seg;
ret -= seg;
if (!buf->len) {
pipe_buf_release(pipe, buf);
tail++;
}
}
if (tail != pipe->tail) {
pipe->tail = tail;
if (pipe->files)
need_wakeup = true;
}
}
out:
pipe_unlock(pipe);
if (need_wakeup)
wakeup_pipe_writers(pipe);
return spliced ?: ret;
}
#endif
static int warn_unsupported(struct file *file, const char *op)
{

2
include/linux/fs.h
View file

@ -2759,8 +2759,6 @@ 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);

2
include/linux/splice.h
View file

@ -84,6 +84,8 @@ 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

26
net/socket.c
View file

@ -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,
};
@ -1066,26 +1064,6 @@ 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)