Re: [PATCH 08/12] mempolicy: remove confusing MPOL_MF_LAZY dead code

[Matthew Wilcox]

On Mon, Sep 25, 2023 at 01:30:51AM -0700, Hugh Dickins wrote:
> v3.8 commit b24f53a0bea3 ("mm: mempolicy: Add MPOL_MF_LAZY") introduced
> MPOL_MF_LAZY, and included it in the MPOL_MF_VALID flags; but a720094ded8
> ("mm: mempolicy: Hide MPOL_NOOP and MPOL_MF_LAZY from userspace for now")
> immediately removed it from MPOL_MF_VALID flags, pending further review.
> "This will need to be revisited", but it has not been reinstated.
> 
> The present state is confusing: there is dead code in mm/mempolicy.c to
> handle MPOL_MF_LAZY cases which can never occur.  Remove that: it can be
> resurrected later if necessary.  But keep the definition of MPOL_MF_LAZY,
> which must remain in the UAPI, even though it always fails with EINVAL.
> 
> https://lore.kernel.org/linux-mm/1553041659-46787-1-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx/
> links to a previous request to remove MPOL_MF_LAZY.
> 
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>

Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>