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

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Date:   Wed, 25 Oct 2023 21:34:15 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Gregory Price <gourry.memverge@...il.com>, linux-mm@...ck.org
Cc:     akpm@...ux-foundation.org, willy@...radead.org, david@...hat.com,
        vbabka@...e.cz, naoya.horiguchi@...ux.dev,
        linux-kernel@...r.kernel.org,
        Gregory Price <gregory.price@...verge.com>
Subject: Re: [PATCH] kpageflags: respect folio head-page flag placement

On Wed, 2023-10-25 at 16:12 -0400, Gregory Price wrote:
> 
> +++ b/fs/proc/page.c
> @@ -188,20 +188,31 @@ u64 stable_page_flags(struct page *page)
>                 u |= 1 << KPF_SLAB;
>  
>         u |= kpf_copy_bit(k, KPF_ERROR,         PG_error);
> -       u |= kpf_copy_bit(k, KPF_DIRTY,         PG_dirty);
> +
> +       if (PageDirty(page))
> +               u |= 1 << KPF_DIRTY;
> +
>         u |= kpf_copy_bit(k, KPF_UPTODATE,      PG_uptodate);
>         u |= kpf_copy_bit(k, KPF_WRITEBACK,     PG_writeback);
>  
> -       u |= kpf_copy_bit(k, KPF_LRU,           PG_lru);
> -       u |= kpf_copy_bit(k, KPF_REFERENCED,    PG_referenced);
> -       u |= kpf_copy_bit(k, KPF_ACTIVE,        PG_active);
> +       if (PageLRU(page))
> +               u |= 1 << KPF_LRU;
> +
> +       if (PageReferenced(page))
> +               u |= 1 << KPF_REFERENCED;
> +
> +       if (PageActive(page))
> +               u |= 1 << KPF_ACTIVE;
> +
>         u |= kpf_copy_bit(k, KPF_RECLAIM,       PG_reclaim);
>  
>         if (PageSwapCache(page))
>                 u |= 1 << KPF_SWAPCACHE;
>         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?

-- 
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