[PATCH net-next 1/2] socket: Allow external sockets to use socket syscalls

[Alex Gartrell <agartrell@fb.com>]

Currently the "is-socket" test for a file compares the ops table pointer,
which is static and local to the socket.c.  Instead, this adds a flag for
private_data_is_socket.  This is an exceptionally long commit message for a
two-line patch.

Signed-off-by: Alex Gartrell <agartrell@fb.com>
---
 include/linux/fs.h | 2 +-
 net/socket.c       | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index bb29b02..d162476 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -809,7 +809,7 @@ struct file {
 #endif
 	/* needed for tty driver, and maybe others */
 	void			*private_data;
-
+	bool			private_data_is_socket : 1;
 #ifdef CONFIG_EPOLL
 	/* Used by fs/eventpoll.c to link all the hooks to this file */
 	struct list_head	f_ep_links;
diff --git a/net/socket.c b/net/socket.c
index 8809afc..cd853be 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -388,6 +388,7 @@ struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname)
 	sock->file = file;
 	file->f_flags = O_RDWR | (flags & O_NONBLOCK);
 	file->private_data = sock;
+	file->private_data_is_socket = true;
 	return file;
 }
 EXPORT_SYMBOL(sock_alloc_file);
@@ -411,7 +412,7 @@ static int sock_map_fd(struct socket *sock, int flags)
 
 struct socket *sock_from_file(struct file *file, int *err)
 {
-	if (file->f_op == &socket_file_ops)
+	if (file->private_data_is_socket)
 		return file->private_data;	/* set in sock_map_fd */
 
 	*err = -ENOTSOCK;
-- 
Alex Gartrell <agartrell@fb.com>