readdir callback error code

Hello,

I noticed following in ext4_readdir() and in other file systems..

filldir returns error in "error": error = filldir(dirent, de->name, ...)

But function itself returns "ret"

What I can see is that when filldir fails, ext4_readir quits, but with
no error....

while (!error && !stored && filp->f_pos < inode->i_size) {

Is it by design or an error?

- Dmitry