linux-kernel - Re: [RFC PATCH 05/12] fs/proc/task_mmu: refactor pagemap_pmd

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Message-ID: <d52d9c7b-4c3c-475e-9293-2b13dcf63e24@lucifer.local>
Date: Tue, 28 Oct 2025 17:36:48 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Gregory Price <gourry@...rry.net>
Cc: Jason Gunthorpe <jgg@...pe.ca>, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
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        Baolin Wang <baolin.wang@...ux.alibaba.com>,
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Subject: Re: [RFC PATCH 05/12] fs/proc/task_mmu: refactor pagemap_pmd_range()

On Tue, Oct 28, 2025 at 09:09:01AM -0400, Gregory Price wrote:
> On Tue, Oct 28, 2025 at 09:52:44AM -0300, Jason Gunthorpe wrote:
> > On Mon, Oct 27, 2025 at 04:38:05PM +0000, Lorenzo Stoakes wrote:
> >
> > The union helps encode in the type system what code is operating on
> > what type of the leaf entry.
> >
> > It seems pretty simple.
> >
>
> My recommendation of a union was a joke and is anything but simple.
>
> Switching to a union now means every current toucher of a swp_entry_t
> needs functions to do conversions to/from that thing as it gets passed
> around to various subsystems. It increases overall complexity for no
> value, i.e. "for negative value".

This is the point I was trying to make yes.

>
> Please do not do this, I regret making the joke.

Never joke on list is the lesson here :)

I have had to learn that the hard way myself...

>
> Regards,
> Gregory

Cheers, Lorenzo