Re: [PATCH -next v3 2/2] sunrpc: Use no_printk() in dfprintk*() dummies

[Geert Uytterhoeven]

On Mon, Oct 16, 2023 at 3:09 PM Geert Uytterhoeven
<geert+renesas@xxxxxxxxx> 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 unconditionally, 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.
>
> This requires removing the protection by CONFIG_SUNRPC_DEBUG of the
> declaration of nlmdbg_cookie2a() in fs/lockd/svclock.c, as its reference
> is now visible to the compiler, but optimized away.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>

> --- 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

I discovered a new build issue related to the use of RPC_IFDEBUG()
in fs/nfsd/nfsfh.c. So there will be a v4...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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