linux-kernel - Re: [PATCH] sunrpc: Use no_printk() in dfprintk*() dummies

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Date:   Wed, 11 Oct 2023 12:40:21 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>, Neil Brown <neilb@...e.de>,
        Olga Kornievskaia <kolga@...app.com>,
        Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>, linux-nfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sunrpc: Use no_printk() in dfprintk*() dummies

On Wed, Oct 11, 2023 at 12:07 PM Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
> When building NFS with W=1 and CONFIG_WERROR=y, but
> CONFIG_SUNRPC_DEBUG=n:
>
>     fs/nfs/nfs4proc.c: In function ‘nfs4_proc_create_session’:
>     fs/nfs/nfs4proc.c:9276:19: error: variable ‘ptr’ set but not used [-Werror=unused-but-set-variable]
>      9276 |         unsigned *ptr;
>           |                   ^~~
>       CC      fs/nfs/callback.o
>     fs/nfs/callback.c: In function ‘nfs41_callback_svc’:
>     fs/nfs/callback.c:98:13: error: variable ‘error’ set but not used [-Werror=unused-but-set-variable]
>        98 |         int error;
>           |             ^~~~~
>       CC      fs/nfs/flexfilelayout/flexfilelayout.o
>     fs/nfs/flexfilelayout/flexfilelayout.c: In function ‘ff_layout_io_track_ds_error’:
>     fs/nfs/flexfilelayout/flexfilelayout.c:1230:13: error: variable ‘err’ set but not used [-Werror=unused-but-set-variable]
>      1230 |         int err;
>           |             ^~~
>       CC      fs/nfs/flexfilelayout/flexfilelayoutdev.o
>     fs/nfs/flexfilelayout/flexfilelayoutdev.c: In function ‘nfs4_ff_alloc_deviceid_node’:
>     fs/nfs/flexfilelayout/flexfilelayoutdev.c:55:16: error: variable ‘ret’ set but not used [-Werror=unused-but-set-variable]
>        55 |         int i, ret = -ENOMEM;
>           |                ^~~
>
> All these are due to variables that are set uncontionally, but are used
> only when debugging is enabled.
>
> Fix this by changing the dfprintk*() dummy macros from empty loops to
> calls to the no_printk() helper.  This informs the compiler that the
> passed debug parameters are actually used, and enables format specifier
> checking as a bonus.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
>  include/linux/sunrpc/debug.h | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/sunrpc/debug.h b/include/linux/sunrpc/debug.h
> index f6aeed07fe04e3d5..76539c6673f2fb15 100644
> --- a/include/linux/sunrpc/debug.h
> +++ b/include/linux/sunrpc/debug.h
> @@ -67,9 +67,9 @@ do {                                                                  \
>  # define RPC_IFDEBUG(x)                x
>  #else
>  # define ifdebug(fac)          if (0)
> -# define dfprintk(fac, fmt, ...)       do {} while (0)
> -# define dfprintk_cont(fac, fmt, ...)  do {} while (0)
> -# define dfprintk_rcu(fac, fmt, ...)   do {} while (0)
> +# define dfprintk(fac, fmt, ...)       no_printk(fmt, ##__VA_ARGS__)
> +# define dfprintk_cont(fac, fmt, ...)  no_printk(fmt, ##__VA_ARGS__)
> +# define dfprintk_rcu(fac, fmt, ...)   no_printk(fmt, ##__VA_ARGS__)
>  # define RPC_IFDEBUG(x)
>  #endif

Bummer, this is causing issues in fs/lockd/svclock.c
Will fix in v2.

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