linux-kernel - Re: [PATCH/RFC] nfs: NFS_SWAP should depend on SWAP

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Message-ID: <CAMuHMdVexUY+SsC7R4-cm7Dj7U62moBUiOs9c2ZbUzvAsU36JQ@mail.gmail.com>
Date:   Mon, 30 Dec 2019 16:55:00 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     "open list:NFS, SUNRPC, AND..." <linux-nfs@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH/RFC] nfs: NFS_SWAP should depend on SWAP

On Mon, Dec 30, 2019 at 4:32 PM Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
> If CONFIG_SWAP=n, it does not make much sense to offer the user the
> option to enable support for swapping over NFS, as that will still fail
> at run time:
>
>     # swapon /swap
>     swapon: /swap: swapon failed: Function not implemented
>
> Fix this by adding a dependency on CONFIG_SWAP.
>
> Fixes: a564b8f0398636ba ("nfs: enable swap on NFS")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
> Marked RFC, as this still doesn't seem to work.
> When enabled, the kernel log is spammed with:
>
>     [  449.371536] __swap_writepage: 413288 callbacks suppressed
>     [  449.371577] Write error on dio swapfile (10047488)
>     [  449.382435] Write error on dio swapfile (14147584)
>     [  449.387320] Write error on dio swapfile (10919936)
>     [  449.392474] Write error on dio swapfile (8945664)
>     [  449.397263] Write error on dio swapfile (24256512)
>     [  449.402330] Write error on dio swapfile (14307328)
>     [  449.407195] Write error on dio swapfile (229376)
>     [  449.412031] Write error on dio swapfile (10293248)
>     [  449.416891] Write error on dio swapfile (2007040)

FWIW, swap over /dev/loop0 using a file on nfsroot also doesn't work: system
hangs, but is still reponsive to ping.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds