linux-kernel - Re: [GIT PULL] VFIO updates for v6.17-rc1

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Message-ID: <CAHk-=wiQ=9g=+A8LPWhPj9yRXFzf=tJKw1Cy-wpj1N9FKu-65w@mail.gmail.com>
Date: Tue, 5 Aug 2025 16:15:15 +0300
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: David Hildenbrand <david@...hat.com>
Cc: Jason Gunthorpe <jgg@...dia.com>, Alex Williamson <alex.williamson@...hat.com>, 
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"lizhe.67@...edance.com" <lizhe.67@...edance.com>
Subject: Re: [GIT PULL] VFIO updates for v6.17-rc1

On Tue, 5 Aug 2025 at 16:05, David Hildenbrand <david@...hat.com> wrote:
>
> So I don't like the idea of micro-optimizing num_pages_contiguous() by
> adding weird tweaks to the core for that.

Seriously - take a look at that suggested sequence I posted, and tell
me that it isn't *MORE* obvious than the horror that is nth_page().

Honestly, if anybody thinks nth_page() is obvious and good, I think
they have some bad case of Stockholm syndrome.

This isn't about micro-optimizing. This is about not writing complete
garbage code that makes no sense.

nth_page() is a disgusting thing that is designed to look up
known-contiguous pages. That code mis-used it for *testing* for being
contiguous. It may have _worked_, but it was the wrong thing to do.

nth_page() in general should just not exist. I don't actually believe
there is any valid reason for it. I do not believe we should actually
have valid consecutive allocations of pages across sections.

So please work on removing that eldritch horror, not adding new worse
versions of it.

           Linus