linux-kernel - Re: [PATCH 02/17] mm: stub out all of swapops.h for !CONFIG

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Date:   Fri, 14 Jun 2019 11:48:47 +0200
From:   Christoph Hellwig <hch@....de>
To:     Vladimir Murzin <vladimir.murzin@....com>
Cc:     Christoph Hellwig <hch@....de>, Palmer Dabbelt <palmer@...ive.com>,
        Damien Le Moal <damien.lemoal@....com>,
        linux-riscv@...ts.infradead.org, uclinux-dev@...inux.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/17] mm: stub out all of swapops.h for !CONFIG_MMU

On Tue, Jun 11, 2019 at 03:36:53PM +0100, Vladimir Murzin wrote:
> It looks like NOMMU ports tend to define those. For ARM they are:
> 
> #define __swp_type(x)           (0)
> #define __swp_offset(x)         (0)
> #define __swp_entry(typ,off)    ((swp_entry_t) { ((typ) | ((off) << 7)) })
> #define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
> #define __swp_entry_to_pte(x)   ((pte_t) { (x).val })
> 
> Anyway, I have no strong opinion on which is better :)

It just seems a lot easier to stub out swapops.h rather than providing
stubs in each arch so that inlines which we are never going to use can
build.  I can look into dropping this from the other nommu ports for
the next merge window, though.