Man page 9 : generic_pipe_buf_get

generic_pipe_buf_get - get a reference to a struct pipe_buffer

void generic_pipe_buf_get(struct pipe_inode_info *  pipe , struct pipe_buffer *  buf );

pipe
    the pipe that the buffer belongs to

buf
    the buffer to get a reference to

This function grabs an extra reference to buf. ItAqs used in in the tee system call, when we duplicate the buffers in one pipe into another.