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Subject[PATCH 3/3] TCP splice receive support
Date
Support for network splice receive.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
include/linux/net.h | 3 +
include/linux/skbuff.h | 5 +
include/net/tcp.h | 3 +
net/core/skbuff.c | 231 ++++++++++++++++++++++++++++++++++++++++++++++++
net/ipv4/af_inet.c | 1 +
net/ipv4/tcp.c | 129 +++++++++++++++++++++++++++
net/socket.c | 13 +++
7 files changed, 385 insertions(+), 0 deletions(-)

diff --git a/include/linux/net.h b/include/linux/net.h
index efc4517..472ee12 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -19,6 +19,7 @@
#define _LINUX_NET_H

#include <linux/wait.h>
+#include <linux/splice.h>
#include <asm/socket.h>

struct poll_table_struct;
@@ -165,6 +166,8 @@ struct proto_ops {
struct vm_area_struct * vma);
ssize_t (*sendpage) (struct socket *sock, struct page *page,
int offset, size_t size, int flags);
+ ssize_t (*splice_read)(struct socket *sock, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len, unsigned int flags);
};

struct net_proto_family {
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index e7367c7..64e3eed 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1504,6 +1504,11 @@ extern int skb_store_bits(struct sk_buff *skb, int offset,
extern __wsum skb_copy_and_csum_bits(const struct sk_buff *skb,
int offset, u8 *to, int len,
__wsum csum);
+extern int skb_splice_bits(struct sk_buff *skb,
+ unsigned int offset,
+ struct pipe_inode_info *pipe,
+ unsigned int len,
+ unsigned int flags);
extern void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
extern void skb_split(struct sk_buff *skb,
struct sk_buff *skb1, const u32 len);
diff --git a/include/net/tcp.h b/include/net/tcp.h
index a8af9ae..8e86697 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -308,6 +308,9 @@ extern int tcp_twsk_unique(struct sock *sk,

extern void tcp_twsk_destructor(struct sock *sk);

+extern ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len, unsigned int flags);
+
static inline void tcp_dec_quickack_mode(struct sock *sk,
const unsigned int pkts)
{
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7c6a34e..daea7b0 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -52,6 +52,7 @@
#endif
#include <linux/string.h>
#include <linux/skbuff.h>
+#include <linux/splice.h>
#include <linux/cache.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
@@ -71,6 +72,40 @@
static struct kmem_cache *skbuff_head_cache __read_mostly;
static struct kmem_cache *skbuff_fclone_cache __read_mostly;

+static void sock_pipe_buf_release(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct sk_buff *skb = (struct sk_buff *) buf->private;
+
+ kfree_skb(skb);
+}
+
+static void sock_pipe_buf_get(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ struct sk_buff *skb = (struct sk_buff *) buf->private;
+
+ skb_get(skb);
+}
+
+static int sock_pipe_buf_steal(struct pipe_inode_info *pipe,
+ struct pipe_buffer *buf)
+{
+ return 1;
+}
+
+
+/* Pipe buffer operations for a socket. */
+static struct pipe_buf_operations sock_pipe_buf_ops = {
+ .can_merge = 0,
+ .map = generic_pipe_buf_map,
+ .unmap = generic_pipe_buf_unmap,
+ .pin = generic_pipe_buf_pin,
+ .release = sock_pipe_buf_release,
+ .steal = sock_pipe_buf_steal,
+ .get = sock_pipe_buf_get,
+};
+
/*
* Keep out-of-line to prevent kernel bloat.
* __builtin_return_address is not used because it is not always
@@ -1116,6 +1151,202 @@ fault:
return -EFAULT;
}

+/*
+ * Callback from splice_to_pipe(), if we need to release some pages
+ * at the end of the spd in case we error'ed out in filling the pipe.
+ */
+static void sock_spd_release(struct splice_pipe_desc *spd, unsigned int i)
+{
+ struct sk_buff *skb = (struct sk_buff *) spd->partial[i].private;
+
+ kfree_skb(skb);
+}
+
+/*
+ * Fill page/offset/length into spd, if it can hold more pages.
+ */
+static inline int spd_fill_page(struct splice_pipe_desc *spd, struct page *page,
+ unsigned int len, unsigned int offset,
+ struct sk_buff *skb)
+{
+ if (unlikely(spd->nr_pages == PIPE_BUFFERS))
+ return 1;
+
+ spd->pages[spd->nr_pages] = page;
+ spd->partial[spd->nr_pages].len = len;
+ spd->partial[spd->nr_pages].offset = offset;
+ spd->partial[spd->nr_pages].private = (unsigned long) skb_get(skb);
+ spd->nr_pages++;
+ return 0;
+}
+
+/*
+ * Map linear and fragment data from the skb to spd. Returns number of
+ * pages mapped.
+ */
+static int __skb_splice_bits(struct sk_buff *skb, unsigned int *offset,
+ unsigned int *total_len,
+ struct splice_pipe_desc *spd)
+{
+ unsigned int nr_pages = spd->nr_pages;
+ unsigned int poff, plen, len, toff, tlen;
+ int headlen, seg;
+
+ toff = *offset;
+ tlen = *total_len;
+ if (!tlen)
+ goto err;
+
+ /*
+ * if the offset is greater than the linear part, go directly to
+ * the fragments.
+ */
+ headlen = skb_headlen(skb);
+ if (toff >= headlen) {
+ toff -= headlen;
+ goto map_frag;
+ }
+
+ /*
+ * first map the linear region into the pages/partial map, skipping
+ * any potential initial offset.
+ */
+ len = 0;
+ while (len < headlen) {
+ void *p = skb->data + len;
+
+ poff = (unsigned long) p & (PAGE_SIZE - 1);
+ plen = min_t(unsigned int, headlen - len, PAGE_SIZE - poff);
+ len += plen;
+
+ if (toff) {
+ if (plen <= toff) {
+ toff -= plen;
+ continue;
+ }
+ plen -= toff;
+ poff += toff;
+ toff = 0;
+ }
+
+ plen = min(plen, tlen);
+ if (!plen)
+ break;
+
+ /*
+ * just jump directly to update and return, no point
+ * in going over fragments when the output is full.
+ */
+ if (spd_fill_page(spd, virt_to_page(p), plen, poff, skb))
+ goto done;
+
+ tlen -= plen;
+ }
+
+ /*
+ * then map the fragments
+ */
+map_frag:
+ for (seg = 0; seg < skb_shinfo(skb)->nr_frags; seg++) {
+ const skb_frag_t *f = &skb_shinfo(skb)->frags[seg];
+
+ plen = f->size;
+ poff = f->page_offset;
+
+ if (toff) {
+ if (plen <= toff) {
+ toff -= plen;
+ continue;
+ }
+ plen -= toff;
+ poff += toff;
+ toff = 0;
+ }
+
+ plen = min(plen, tlen);
+ if (!plen)
+ break;
+
+ if (spd_fill_page(spd, f->page, plen, poff, skb))
+ break;
+
+ tlen -= plen;
+ }
+
+done:
+ if (spd->nr_pages - nr_pages) {
+ *offset = 0;
+ *total_len = tlen;
+ return 0;
+ }
+err:
+ return 1;
+}
+
+/*
+ * Map data from the skb to a pipe. Should handle both the linear part,
+ * the fragments, and the frag list. It does NOT handle frag lists within
+ * the frag list, if such a thing exists. We'd probably need to recurse to
+ * handle that cleanly.
+ */
+int skb_splice_bits(struct sk_buff *__skb, unsigned int offset,
+ struct pipe_inode_info *pipe, unsigned int tlen,
+ unsigned int flags)
+{
+ struct partial_page partial[PIPE_BUFFERS];
+ struct page *pages[PIPE_BUFFERS];
+ struct splice_pipe_desc spd = {
+ .pages = pages,
+ .partial = partial,
+ .flags = flags,
+ .ops = &sock_pipe_buf_ops,
+ .spd_release = sock_spd_release,
+ };
+ struct sk_buff *skb;
+
+ /*
+ * I'd love to avoid the clone here, but tcp_read_sock()
+ * ignores reference counts and unconditonally kills the sk_buff
+ * on return from the actor.
+ */
+ skb = skb_clone(__skb, GFP_KERNEL);
+ if (unlikely(!skb))
+ return -ENOMEM;
+
+ /*
+ * __skb_splice_bits() only fails if the output has no room left,
+ * so no point in going over the frag_list for the error case.
+ */
+ if (__skb_splice_bits(skb, &offset, &tlen, &spd))
+ goto done;
+ else if (!tlen)
+ goto done;
+
+ /*
+ * now see if we have a frag_list to map
+ */
+ if (skb_shinfo(skb)->frag_list) {
+ struct sk_buff *list = skb_shinfo(skb)->frag_list;
+
+ for (; list && tlen; list = list->next) {
+ if (__skb_splice_bits(list, &offset, &tlen, &spd))
+ break;
+ }
+ }
+
+done:
+ /*
+ * drop our reference to the clone, the pipe consumption will
+ * drop the rest.
+ */
+ kfree_skb(skb);
+
+ if (spd.nr_pages)
+ return splice_to_pipe(pipe, &spd);
+
+ return 0;
+}
+
/**
* skb_store_bits - store bits from kernel buffer to skb
* @skb: destination buffer
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 041fba3..0ff9f86 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -835,6 +835,7 @@ const struct proto_ops inet_stream_ops = {
.recvmsg = sock_common_recvmsg,
.mmap = sock_no_mmap,
.sendpage = tcp_sendpage,
+ .splice_read = tcp_splice_read,
#ifdef CONFIG_COMPAT
.compat_setsockopt = compat_sock_common_setsockopt,
.compat_getsockopt = compat_sock_common_getsockopt,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 450f44b..63efd7a 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -253,6 +253,10 @@
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/fs.h>
+#include <linux/skbuff.h>
+#include <linux/splice.h>
+#include <linux/net.h>
+#include <linux/socket.h>
#include <linux/random.h>
#include <linux/bootmem.h>
#include <linux/cache.h>
@@ -264,6 +268,7 @@
#include <net/xfrm.h>
#include <net/ip.h>
#include <net/netdma.h>
+#include <net/sock.h>

#include <asm/uaccess.h>
#include <asm/ioctls.h>
@@ -291,6 +296,15 @@ EXPORT_SYMBOL(tcp_memory_allocated);
EXPORT_SYMBOL(tcp_sockets_allocated);

/*
+ * TCP splice context
+ */
+struct tcp_splice_state {
+ struct pipe_inode_info *pipe;
+ size_t len;
+ unsigned int flags;
+};
+
+/*
* Pressure flag: try to collapse.
* Technical note: it is used by multiple contexts non atomically.
* All the sk_stream_mem_schedule() is of this nature: accounting
@@ -500,6 +514,120 @@ static inline void tcp_push(struct sock *sk, int flags, int mss_now,
}
}

+int tcp_splice_data_recv(read_descriptor_t *rd_desc, struct sk_buff *skb,
+ unsigned int offset, size_t len)
+{
+ struct tcp_splice_state *tss = rd_desc->arg.data;
+
+ return skb_splice_bits(skb, offset, tss->pipe, tss->len, tss->flags);
+}
+
+static int __tcp_splice_read(struct sock *sk, struct tcp_splice_state *tss)
+{
+ /* Store TCP splice context information in read_descriptor_t. */
+ read_descriptor_t rd_desc = {
+ .arg.data = tss,
+ };
+
+ return tcp_read_sock(sk, &rd_desc, tcp_splice_data_recv);
+}
+
+/**
+ * tcp_splice_read - splice data from TCP socket to a pipe
+ * @sock: socket to splice from
+ * @ppos: position (not valid)
+ * @pipe: pipe to splice to
+ * @len: number of bytes to splice
+ * @flags: splice modifier flags
+ *
+ * Description:
+ * Will read pages from given socket and fill them into a pipe.
+ *
+ **/
+ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len,
+ unsigned int flags)
+{
+ struct sock *sk = sock->sk;
+ struct tcp_splice_state tss = {
+ .pipe = pipe,
+ .len = len,
+ .flags = flags,
+ };
+ long timeo;
+ ssize_t spliced;
+ int ret;
+
+ /*
+ * We can't seek on a socket input
+ */
+ if (unlikely(*ppos))
+ return -ESPIPE;
+
+ ret = spliced = 0;
+
+ lock_sock(sk);
+
+ timeo = sock_rcvtimeo(sk, flags & SPLICE_F_NONBLOCK);
+ while (tss.len) {
+ ret = __tcp_splice_read(sk, &tss);
+ if (ret < 0)
+ break;
+ else if (!ret) {
+ if (spliced)
+ break;
+ if (flags & SPLICE_F_NONBLOCK) {
+ ret = -EAGAIN;
+ break;
+ }
+ if (sock_flag(sk, SOCK_DONE))
+ break;
+ if (sk->sk_err) {
+ ret = sock_error(sk);
+ break;
+ }
+ if (sk->sk_shutdown & RCV_SHUTDOWN)
+ break;
+ if (sk->sk_state == TCP_CLOSE) {
+ /*
+ * This occurs when user tries to read
+ * from never connected socket.
+ */
+ if (!sock_flag(sk, SOCK_DONE))
+ ret = -ENOTCONN;
+ break;
+ }
+ if (!timeo) {
+ ret = -EAGAIN;
+ break;
+ }
+ sk_wait_data(sk, &timeo);
+ if (signal_pending(current)) {
+ ret = sock_intr_errno(timeo);
+ break;
+ }
+ continue;
+ }
+ tss.len -= ret;
+ spliced += ret;
+
+ release_sock(sk);
+ lock_sock(sk);
+
+ if (sk->sk_err || sk->sk_state == TCP_CLOSE ||
+ (sk->sk_shutdown & RCV_SHUTDOWN) || !timeo ||
+ signal_pending(current))
+ break;
+ }
+
+ release_sock(sk);
+
+ if (spliced)
+ return spliced;
+
+ return ret;
+}
+
static ssize_t do_tcp_sendpages(struct sock *sk, struct page **pages, int poffset,
size_t psize, int flags)
{
@@ -2515,6 +2643,7 @@ EXPORT_SYMBOL(tcp_poll);
EXPORT_SYMBOL(tcp_read_sock);
EXPORT_SYMBOL(tcp_recvmsg);
EXPORT_SYMBOL(tcp_sendmsg);
+EXPORT_SYMBOL(tcp_splice_read);
EXPORT_SYMBOL(tcp_sendpage);
EXPORT_SYMBOL(tcp_setsockopt);
EXPORT_SYMBOL(tcp_shutdown);
diff --git a/net/socket.c b/net/socket.c
index f453019..41240f5 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -111,6 +111,9 @@ static long compat_sock_ioctl(struct file *file,
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);

/*
* Socket files have a set of 'special' operations as well as the generic file ones. These don't appear
@@ -133,6 +136,7 @@ static const struct file_operations socket_file_ops = {
.fasync = sock_fasync,
.sendpage = sock_sendpage,
.splice_write = generic_splice_sendpage,
+ .splice_read = sock_splice_read,
};

/*
@@ -691,6 +695,15 @@ static ssize_t sock_sendpage(struct file *file, struct page *page,
return sock->ops->sendpage(sock, page, offset, size, flags);
}

+static ssize_t sock_splice_read(struct file *file, loff_t *ppos,
+ struct pipe_inode_info *pipe, size_t len,
+ unsigned int flags)
+{
+ struct socket *sock = file->private_data;
+
+ return sock->ops->splice_read(sock, ppos, pipe, len, flags);
+}
+
static struct sock_iocb *alloc_sock_iocb(struct kiocb *iocb,
struct sock_iocb *siocb)
{
--
1.5.2.1.174.gcd03
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