Re: [RFC 3/3] mm/vma: Introduce some more VMA flag wrappers

[Hugh Dickins]

On Mon, 2 Mar 2020, Anshuman Khandual wrote:

> This adds the following new VMA flag wrappers which will replace current
> open encodings across various places. This should not have any functional
> implications.
> 
> vma_is_dontdump()
> vma_is_noreserve()
> vma_is_special()
> vma_is_locked()
> vma_is_mergeable()
> vma_is_softdirty()
> vma_is_thp()
> vma_is_nothp()

Why?? Please don't. I am not at all keen on your 1/3 and 2/3 (some
of us actually like to see what the VM_ flags are where they're used,
without having to chase through scattered wrappers hiding them),
but this 3/3 particularly upset me.

There is a good reason for the (hideously named) is_vm_hugetlb_page(vma):
to save "#ifdef CONFIG_HUGETLB_PAGE"s all over (though I suspect the
same could have been achieved much more nicely by #define VM_HUGETLB 0);
but hiding all flags in vma_is_whatever()s is counter-productive churn.

Improved readability? Not to my eyes.

Hugh