=== modified file 'include/linux/mm_types.h'
--- old/include/linux/mm_types.h	2012-03-19 23:46:01 +0000
+++ new/include/linux/mm_types.h	2012-03-23 21:39:19 +0000
@@ -149,6 +149,17 @@ struct page {
 	 */
 	void *shadow;
 #endif
+
+#if defined(CONFIG_TCP_ZERO_COPY_TRANSFER_COMPLETION_NOTIFICATION)
+	/*
+	 * Used to implement support for notification on zero-copy TCP transfer
+	 * completion. It might look as not good to have this field here and
+	 * it's better to have it in struct sk_buff, but it would make the code
+	 * much more complicated and fragile, since all skb then would have to
+	 * contain only pages with the same value in this field.
+	 */
+	 void *net_priv;
+#endif
 }
 /*
  * The struct page can be forced to be double word aligned so that atomic ops

=== modified file 'include/linux/net.h'
--- old/include/linux/net.h	2012-03-19 23:46:01 +0000
+++ new/include/linux/net.h	2012-03-23 21:39:19 +0000
@@ -61,6 +61,7 @@ typedef enum {
 #include <linux/fcntl.h>	/* For O_CLOEXEC and O_NONBLOCK */
 #include <linux/kmemcheck.h>
 #include <linux/rcupdate.h>
+#include <linux/mm.h>
 
 struct poll_table_struct;
 struct pipe_inode_info;
@@ -289,5 +290,44 @@ extern int kernel_sock_shutdown(struct s
 	MODULE_ALIAS("net-pf-" __stringify(pf) "-proto-" __stringify(proto) \
 		     "-type-" __stringify(type))
 
+#if defined(CONFIG_TCP_ZERO_COPY_TRANSFER_COMPLETION_NOTIFICATION)
+/* Support for notification on zero-copy TCP transfer completion */
+typedef void (*net_get_page_callback_t)(struct page *page);
+typedef void (*net_put_page_callback_t)(struct page *page);
+
+extern net_get_page_callback_t net_get_page_callback;
+extern net_put_page_callback_t net_put_page_callback;
+
+extern int net_set_get_put_page_callbacks(
+	net_get_page_callback_t get_callback,
+	net_put_page_callback_t put_callback);
+
+/*
+ * See comment for net_set_get_put_page_callbacks() why those functions
+ * don't need any protection.
+ */
+static inline void net_get_page(struct page *page)
+{
+	if (page->net_priv != 0)
+		net_get_page_callback(page);
+	get_page(page);
+}
+static inline void net_put_page(struct page *page)
+{
+	if (page->net_priv != 0)
+		net_put_page_callback(page);
+	put_page(page);
+}
+#else
+static inline void net_get_page(struct page *page)
+{
+	get_page(page);
+}
+static inline void net_put_page(struct page *page)
+{
+	put_page(page);
+}
+#endif /* CONFIG_TCP_ZERO_COPY_TRANSFER_COMPLETION_NOTIFICATION */
+
 #endif /* __KERNEL__ */
 #endif	/* _LINUX_NET_H */

=== modified file 'include/linux/skbuff.h'
--- old/include/linux/skbuff.h	2012-03-19 23:46:01 +0000
+++ new/include/linux/skbuff.h	2012-03-23 21:39:19 +0000
@@ -1702,7 +1702,7 @@ static inline struct page *skb_frag_page
  */
 static inline void __skb_frag_ref(skb_frag_t *frag)
 {
-	get_page(skb_frag_page(frag));
+	net_get_page(skb_frag_page(frag));
 }
 
 /**
@@ -1725,7 +1725,7 @@ static inline void skb_frag_ref(struct s
  */
 static inline void __skb_frag_unref(skb_frag_t *frag)
 {
-	put_page(skb_frag_page(frag));
+	net_put_page(skb_frag_page(frag));
 }
 
 /**

=== modified file 'net/Kconfig'
--- old/net/Kconfig	2012-03-19 23:46:01 +0000
+++ new/net/Kconfig	2012-03-23 21:39:19 +0000
@@ -72,6 +72,18 @@ config INET
 
 	  Short answer: say Y.
 
+config TCP_ZERO_COPY_TRANSFER_COMPLETION_NOTIFICATION
+	bool "TCP/IP zero-copy transfer completion notification"
+        depends on INET
+        default SCST_ISCSI
+	---help---
+	  Adds support for sending a notification upon completion of a
+          zero-copy TCP/IP transfer. This can speed up certain TCP/IP
+          software. Currently this is only used by the iSCSI target driver
+          iSCSI-SCST.
+
+          If unsure, say N.
+
 if INET
 source "net/ipv4/Kconfig"
 source "net/ipv6/Kconfig"

=== modified file 'net/core/skbuff.c'
--- old/net/core/skbuff.c	2012-03-19 23:46:01 +0000
+++ new/net/core/skbuff.c	2012-03-23 21:39:19 +0000
@@ -77,13 +77,13 @@ static struct kmem_cache *skbuff_fclone_
 static void sock_pipe_buf_release(struct pipe_inode_info *pipe,
 				  struct pipe_buffer *buf)
 {
-	put_page(buf->page);
+	net_put_page(buf->page);
 }
 
 static void sock_pipe_buf_get(struct pipe_inode_info *pipe,
 				struct pipe_buffer *buf)
 {
-	get_page(buf->page);
+	net_get_page(buf->page);
 }
 
 static int sock_pipe_buf_steal(struct pipe_inode_info *pipe,
@@ -702,7 +702,7 @@ int skb_copy_ubufs(struct sk_buff *skb,
 		if (!page) {
 			while (head) {
 				struct page *next = (struct page *)head->private;
-				put_page(head);
+				net_put_page(head);
 				head = next;
 			}
 			return -ENOMEM;
@@ -1542,7 +1542,7 @@ EXPORT_SYMBOL(skb_copy_bits);
  */
 static void sock_spd_release(struct splice_pipe_desc *spd, unsigned int i)
 {
-	put_page(spd->pages[i]);
+	net_put_page(spd->pages[i]);
 }
 
 static inline struct page *linear_to_page(struct page *page, unsigned int *len,
@@ -1566,7 +1566,7 @@ new_page:
 		off = sk->sk_sndmsg_off;
 		mlen = PAGE_SIZE - off;
 		if (mlen < 64 && mlen < *len) {
-			put_page(p);
+			net_put_page(p);
 			goto new_page;
 		}
 
@@ -1576,7 +1576,7 @@ new_page:
 	memcpy(page_address(p) + off, page_address(page) + *offset, *len);
 	sk->sk_sndmsg_off += *len;
 	*offset = off;
-	get_page(p);
+	net_get_page(p);
 
 	return p;
 }
@@ -1598,7 +1598,7 @@ static inline int spd_fill_page(struct s
 		if (!page)
 			return 1;
 	} else
-		get_page(page);
+		net_get_page(page);
 
 	spd->pages[spd->nr_pages] = page;
 	spd->partial[spd->nr_pages].len = *len;

=== modified file 'net/ipv4/Makefile'
--- old/net/ipv4/Makefile	2012-03-19 23:46:01 +0000
+++ new/net/ipv4/Makefile	2012-03-23 21:39:19 +0000
@@ -50,6 +50,7 @@ obj-$(CONFIG_TCP_CONG_YEAH) += tcp_yeah.
 obj-$(CONFIG_TCP_CONG_ILLINOIS) += tcp_illinois.o
 obj-$(CONFIG_CGROUP_MEM_RES_CTLR_KMEM) += tcp_memcontrol.o
 obj-$(CONFIG_NETLABEL) += cipso_ipv4.o
+obj-$(CONFIG_TCP_ZERO_COPY_TRANSFER_COMPLETION_NOTIFICATION) += tcp_zero_copy.o
 
 obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
 		      xfrm4_output.o

=== modified file 'net/ipv4/ip_output.c'
--- old/net/ipv4/ip_output.c	2012-03-19 23:46:01 +0000
+++ new/net/ipv4/ip_output.c	2012-03-23 21:39:19 +0000
@@ -1246,7 +1246,7 @@ ssize_t	ip_append_page(struct sock *sk,
 		if (skb_can_coalesce(skb, i, page, offset)) {
 			skb_frag_size_add(&skb_shinfo(skb)->frags[i-1], len);
 		} else if (i < MAX_SKB_FRAGS) {
-			get_page(page);
+			net_get_page(page);
 			skb_fill_page_desc(skb, i, page, offset, len);
 		} else {
 			err = -EMSGSIZE;

=== modified file 'net/ipv4/tcp.c'
--- old/net/ipv4/tcp.c	2012-03-19 23:46:01 +0000
+++ new/net/ipv4/tcp.c	2012-03-23 21:39:19 +0000
@@ -813,7 +813,7 @@ new_segment:
 		if (can_coalesce) {
 			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
 		} else {
-			get_page(page);
+			net_get_page(page);
 			skb_fill_page_desc(skb, i, page, offset, copy);
 		}
 
@@ -1025,7 +1025,7 @@ new_segment:
 					goto new_segment;
 				} else if (page) {
 					if (off == PAGE_SIZE) {
-						put_page(page);
+						net_put_page(page);
 						sk->sk_sndmsg_page = page = NULL;
 						off = 0;
 					}
@@ -1065,9 +1065,9 @@ new_segment:
 				} else {
 					skb_fill_page_desc(skb, i, page, off, copy);
 					if (sk->sk_sndmsg_page) {
-						get_page(page);
+						net_get_page(page);
 					} else if (off + copy < PAGE_SIZE) {
-						get_page(page);
+						net_get_page(page);
 						sk->sk_sndmsg_page = page;
 					}
 				}

=== added file 'net/ipv4/tcp_zero_copy.c'
--- old/net/ipv4/tcp_zero_copy.c	1970-01-01 00:00:00 +0000
+++ new/net/ipv4/tcp_zero_copy.c	2012-03-23 21:39:19 +0000
@@ -0,0 +1,50 @@
+/*
+ *	Support routines for TCP zero copy transmit
+ *
+ *	Created by Vladislav Bolkhovitin
+ *
+ *	This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      version 2 as published by the Free Software Foundation.
+ */
+
+#include <linux/export.h>
+#include <linux/skbuff.h>
+
+net_get_page_callback_t net_get_page_callback __read_mostly;
+EXPORT_SYMBOL_GPL(net_get_page_callback);
+
+net_put_page_callback_t net_put_page_callback __read_mostly;
+EXPORT_SYMBOL_GPL(net_put_page_callback);
+
+/*
+ * Caller of this function must ensure that at the moment when it's called
+ * there are no pages in the system with net_priv field set to non-zero
+ * value. Hence, this function, as well as net_get_page() and net_put_page(),
+ * don't need any protection.
+ */
+int net_set_get_put_page_callbacks(
+	net_get_page_callback_t get_callback,
+	net_put_page_callback_t put_callback)
+{
+	int res = 0;
+
+	if ((net_get_page_callback != NULL) && (get_callback != NULL) &&
+	    (net_get_page_callback != get_callback)) {
+		res = -EBUSY;
+		goto out;
+	}
+
+	if ((net_put_page_callback != NULL) && (put_callback != NULL) &&
+	    (net_put_page_callback != put_callback)) {
+		res = -EBUSY;
+		goto out;
+	}
+
+	net_get_page_callback = get_callback;
+	net_put_page_callback = put_callback;
+
+out:
+	return res;
+}
+EXPORT_SYMBOL_GPL(net_set_get_put_page_callbacks);

