mm: export generic_pipe_buf_*() to modules

This is needed by fuse device code which wants to create pipe buffers.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/fs/pipe.c b/fs/pipe.c
index d79872e..8912fa8 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -230,6 +230,7 @@
 
 	return kmap(buf->page);
 }
+EXPORT_SYMBOL(generic_pipe_buf_map);
 
 /**
  * generic_pipe_buf_unmap - unmap a previously mapped pipe buffer
@@ -249,6 +250,7 @@
 	} else
 		kunmap(buf->page);
 }
+EXPORT_SYMBOL(generic_pipe_buf_unmap);
 
 /**
  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
@@ -279,6 +281,7 @@
 
 	return 1;
 }
+EXPORT_SYMBOL(generic_pipe_buf_steal);
 
 /**
  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
@@ -294,6 +297,7 @@
 {
 	page_cache_get(buf->page);
 }
+EXPORT_SYMBOL(generic_pipe_buf_get);
 
 /**
  * generic_pipe_buf_confirm - verify contents of the pipe buffer
@@ -309,6 +313,7 @@
 {
 	return 0;
 }
+EXPORT_SYMBOL(generic_pipe_buf_confirm);
 
 /**
  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
@@ -323,6 +328,7 @@
 {
 	page_cache_release(buf->page);
 }
+EXPORT_SYMBOL(generic_pipe_buf_release);
 
 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 	.can_merge = 1,