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

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>

diff --git a/fs/splice.c b/fs/splice.c
index 3e06611..e337630 100644 (file)
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -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 @@ done:
 
 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;
+
+       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;
 
-EXPORT_SYMBOL(generic_splice_sendpage);
+               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)
 {

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 133f064..df92f4b 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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);
 

diff --git a/include/linux/splice.h b/include/linux/splice.h
index a55179f..991ae31 100644 (file)
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -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

diff --git a/net/socket.c b/net/socket.c
index 3df96e9..c4d9104 100644 (file)
--- 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,
 };
@@ -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)