Re: [PATCH 1/4] bdi: add check for bdi_debug_root

[Jan Kara <jack@suse.cz>]

On Fri 27-10-17 01:35:36, weiping zhang wrote:
> this patch add a check for bdi_debug_root and do error handle for it.
> we should make sure it was created success, otherwise when add new
> block device's bdi folder(eg, 8:0) will be create a debugfs root directory.
> 
> Signed-off-by: weiping zhang <zhangweiping@didichuxing.com>
> ---
>  mm/backing-dev.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)

These functions get called only on system boot - ENOMEM in those cases is
generally considered fatal and oopsing is acceptable result. So I don't
think this patch is needed.

								Honza

> 
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index 74b52dfd5852..5072be19d9b2 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -36,9 +36,12 @@ struct workqueue_struct *bdi_wq;
>  
>  static struct dentry *bdi_debug_root;
>  
> -static void bdi_debug_init(void)
> +static int bdi_debug_init(void)
>  {
>  	bdi_debug_root = debugfs_create_dir("bdi", NULL);
> +	if (!bdi_debug_root)
> +		return -ENOMEM;
> +	return 0;
>  }
>  
>  static int bdi_debug_stats_show(struct seq_file *m, void *v)
> @@ -126,8 +129,9 @@ static void bdi_debug_unregister(struct backing_dev_info *bdi)
>  	debugfs_remove(bdi->debug_dir);
>  }
>  #else
> -static inline void bdi_debug_init(void)
> +static inline int bdi_debug_init(void)
>  {
> +	return 0;
>  }
>  static inline void bdi_debug_register(struct backing_dev_info *bdi,
>  				      const char *name)
> @@ -229,12 +233,19 @@ ATTRIBUTE_GROUPS(bdi_dev);
>  
>  static __init int bdi_class_init(void)
>  {
> +	int ret;
> +
>  	bdi_class = class_create(THIS_MODULE, "bdi");
>  	if (IS_ERR(bdi_class))
>  		return PTR_ERR(bdi_class);
>  
>  	bdi_class->dev_groups = bdi_dev_groups;
> -	bdi_debug_init();
> +	ret = bdi_debug_init();
> +	if (ret) {
> +		class_destroy(bdi_class);
> +		bdi_class = NULL;
> +		return ret;
> +	}
>  
>  	return 0;
>  }
> -- 
> 2.14.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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