linux-kernel - Re: [PATCH] kpageflags: respect folio head-page flag placement

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Date:   Thu, 26 Oct 2023 15:12:41 -0400
From:   Gregory Price <gregory.price@...verge.com>
To:     Rik van Riel <riel@...riel.com>
Cc:     Gregory Price <gourry.memverge@...il.com>, linux-mm@...ck.org,
        akpm@...ux-foundation.org, willy@...radead.org, david@...hat.com,
        vbabka@...e.cz, naoya.horiguchi@...ux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kpageflags: respect folio head-page flag placement

On Wed, Oct 25, 2023 at 09:34:15PM -0400, Rik van Riel wrote:
> On Wed, 2023-10-25 at 16:12 -0400, Gregory Price wrote:
> >         u |= kpf_copy_bit(k, KPF_SWAPBACKED,    PG_swapbacked);
> > 
> 
> Aren't PG_locked, PG_reclaim, and PG_swapbacked also maintained only on
> the folio/head?
> 
> Would it make sense to convert those over as well?
> 

I see them registered as PF_NO_TAIL in include/linux/page-flags.h

Certainly i think there are other updates that are likely needed, but
I wasn't quite sure how to handle ONLY_HEAD and NO_TAIL and other
conditionals.  Should the bits always be 0 or should it refer to HEAD?

Just not sure at the moment.

~Gregory