Re: [PATCH -next v2] sunrpc: Use no_printk() in dfprintk*() dummies

[Jeff Layton <jlayton@kernel.org>]

On Thu, 2023-10-12 at 12:08 +0200, Geert Uytterhoeven 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(), as its reference is now visible to the
> compiler, but optimized away.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> ---
> v2:
>   - s/uncontionally/unconditionally/,
>   - Drop CONFIG_SUNRPC_DEBUG check in fs/lockd/svclock.c to fix build
>     failure.
> ---
>  fs/lockd/svclock.c           | 2 --
>  include/linux/sunrpc/debug.h | 6 +++---
>  2 files changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
> index 43aeba9de55cbbc5..119a0c31d30eed4f 100644
> --- a/fs/lockd/svclock.c
> +++ b/fs/lockd/svclock.c
> @@ -55,7 +55,6 @@ static const struct rpc_call_ops nlmsvc_grant_ops;
>  static LIST_HEAD(nlm_blocked);
>  static DEFINE_SPINLOCK(nlm_blocked_lock);
>  
> -#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
>  static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
>  {
>  	/*
> @@ -82,7 +81,6 @@ static const char *nlmdbg_cookie2a(const struct nlm_cookie *cookie)
>  
>  	return buf;
>  }
> -#endif
>  
>  /*
>   * Insert a blocked lock into the global list
> 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
>  

Acked-by: Jeff Layton <jlayton@kernel.org>