[Question] Dead code in copy_pud_range() for copy_huge_pud() error check?

[Ingyu Jang <ingyujang25@korea.ac.kr>]

Hi,

I noticed that in mm/memory.c, the function copy_pud_range() checks
if copy_huge_pud() returns -ENOMEM (at line 1421):

    err = copy_huge_pud(dst_mm, src_mm,
                        dst_pud, src_pud, addr, src_vma);
    if (err == -ENOMEM)
        return -ENOMEM;

However, looking at copy_huge_pud() in mm/huge_memory.c (line 1966),
it only returns two values:
  - 0 on success (line 1994)
  - -EAGAIN when !pud_trans_huge(pud) (line 1978)

There is no code path that returns -ENOMEM, which means the check
"if (err == -ENOMEM)" at line 1421 is unreachable dead code.

Is this intentional defensive coding for potential future changes,
or could this unreachable error check be cleaned up?

Thanks,
Ingyu Jang