Re: [PATCH v2] bcache: return 0 from bch_debug_init() if CONFIG_DEBUG_FS=n

[Kent Overstreet <kent.overstreet@gmail.com>]

On Thu, May 17, 2018 at 05:53:48PM +0800, Coly Li wrote:
> Commit 539d39eb2708 ("bcache: fix wrong return value in bch_debug_init()")
> returns the return value of debugfs_create_dir() to bcache_init(). When
> CONFIG_DEBUG_FS=n, bch_debug_init() always returns 1 and makes
> bcache_init() failedi.
> 
> This patch makes bch_debug_init() always returns 0 if CONFIG_DEBUG_FS=n,
> so bcache can continue to work for the kernels which don't have debugfs
> enanbled.
> 
> Fixes: Commit 539d39eb2708 ("bcache: fix wrong return value in bch_debug_init()")
> Cc: stable@vger.kernel.org
> Signed-off-by: Coly Li <colyli@suse.de>
> Reported-by: Massimo B. <massimo.b@gmx.net>
> Reported-by: Kai Krakow <kai@kaishome.de>
> Tested-by: Kai Krakow <kai@kaishome.de>
> Cc: Kent Overstreet <kent.overstreet@gmail.com>
> ---
>  drivers/md/bcache/bcache.h | 5 +++++
>  drivers/md/bcache/debug.c  | 8 ++++----
>  2 files changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
> index 3a0cfb237af9..5b3fe87f32ee 100644
> --- a/drivers/md/bcache/bcache.h
> +++ b/drivers/md/bcache/bcache.h
> @@ -994,8 +994,13 @@ void bch_open_buckets_free(struct cache_set *);
>  
>  int bch_cache_allocator_start(struct cache *ca);
>  
> +#ifdef CONFIG_DEBUG_FS

you could just use if (IS_ENABLED(CONFIG_DEBUG_FS)) in bch_debug_init, that way
you don't need to add an #ifdef

>  void bch_debug_exit(void);
>  int bch_debug_init(struct kobject *);
> +#else
> +static inline void bch_debug_exit(void) {};
> +static inline int bch_debug_init(struct kobject *kobj) { return 0; };
> +#endif
>  void bch_request_exit(void);
>  int bch_request_init(void);
>  
> diff --git a/drivers/md/bcache/debug.c b/drivers/md/bcache/debug.c
> index 4e63c6f6c04d..20e5e524e88e 100644
> --- a/drivers/md/bcache/debug.c
> +++ b/drivers/md/bcache/debug.c
> @@ -17,8 +17,6 @@
>  #include <linux/random.h>
>  #include <linux/seq_file.h>
>  
> -struct dentry *bcache_debug;
> -
>  #ifdef CONFIG_BCACHE_DEBUG
>  
>  #define for_each_written_bset(b, start, i)				\
> @@ -151,6 +149,8 @@ void bch_data_verify(struct cached_dev *dc, struct bio *bio)
>  
>  /* XXX: cache set refcounting */
>  
> +struct dentry *bcache_debug;
> +
>  struct dump_iterator {
>  	char			buf[PAGE_SIZE];
>  	size_t			bytes;
> @@ -240,8 +240,6 @@ void bch_debug_init_cache_set(struct cache_set *c)
>  	}
>  }
>  
> -#endif
> -
>  void bch_debug_exit(void)
>  {
>  	if (!IS_ERR_OR_NULL(bcache_debug))
> @@ -254,3 +252,5 @@ int __init bch_debug_init(struct kobject *kobj)
>  
>  	return IS_ERR_OR_NULL(bcache_debug);
>  }
> +
> +#endif
> -- 
> 2.16.3
>