[TCP]: Splice receive support.

Support for network splice receive.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

7 files changed, 401 insertions, 0 deletions

diff --git a/include/linux/net.h b/include/linux/net.h
index 596131ea46f4..0235d917d5c3 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -22,6 +22,7 @@
 #include <asm/socket.h>
 
 struct poll_table_struct;
+struct pipe_inode_info;
 struct inode;
 struct net;
 
@@ -172,6 +173,8 @@ 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 bddd50bd6878..d39f53ef66bb 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -95,6 +95,7 @@
 
 struct net_device;
 struct scatterlist;
+struct pipe_inode_info;
 
 #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
 struct nf_conntrack {
@@ -1559,6 +1560,11 @@ 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 cb5b033e0e59..d893b4480769 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -309,6 +309,9 @@ 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 b6283779e93d..98420f9c4b6d 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,
+        .confirm = generic_pipe_buf_confirm,
+        .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
@@ -1122,6 +1157,217 @@ 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) {
+                int ret;
+
+                /*
+                 * Drop the socket lock, otherwise we have reverse
+                 * locking dependencies between sk_lock and i_mutex
+                 * here as compared to sendfile(). We enter here
+                 * with the socket lock held, and splice_to_pipe() will
+                 * grab the pipe inode lock. For sendfile() emulation,
+                 * we call into ->sendpage() with the i_mutex lock held
+                 * and networking will grab the socket lock.
+                 */
+                release_sock(__skb->sk);
+                ret = splice_to_pipe(pipe, &spd);
+                lock_sock(__skb->sk);
+                return ret;
+        }
+
+        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 d2f22e74b267..c75f20b49935 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -838,6 +838,7 @@ 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 8e65182f7af1..56ed40703f98 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -254,6 +254,10 @@
 #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>
@@ -265,6 +269,7 @@
 #include <net/xfrm.h>
 #include <net/ip.h>
 #include <net/netdma.h>
+#include <net/sock.h>
 
 #include <asm/uaccess.h>
 #include <asm/ioctls.h>
@@ -292,6 +297,15 @@ 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
@@ -501,6 +515,120 @@ 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)
 {
@@ -2532,6 +2660,7 @@ 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 74784dfe8e5b..92fab9e1c602 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -112,6 +112,9 @@ 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
@@ -134,6 +137,7 @@ 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)
 {