Man page 9 : generic_file_splice_write

generic_file_splice_write - splice data from a pipe to a file

ssize_t generic_file_splice_write(struct pipe_inode_info *  pipe , struct file *  out , loff_t *  ppos , size_t  len , unsigned int  flags );

pipe
    pipe info

out
    file to write to

ppos
    position in out

len
    number of bytes to splice

flags
    splice modifier flags

Will either move or copy pages (determined by flags options) from the given pipe inode to the given file.