linux-kernel - Re: [PATCH v6 1/9] fs: Create sb

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Message-ID: <87sehf4lv9.fsf@mailhost.krisman.be>
Date: Mon, 25 Aug 2025 08:38:34 -0400
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: André Almeida <andrealmeid@...lia.com>
Cc: Miklos Szeredi <miklos@...redi.hu>,  Amir Goldstein
 <amir73il@...il.com>,  Theodore Tso <tytso@....edu>,
  linux-unionfs@...r.kernel.org,  linux-kernel@...r.kernel.org,
  linux-fsdevel@...r.kernel.org,  Alexander Viro <viro@...iv.linux.org.uk>,
  Christian Brauner <brauner@...nel.org>,  Jan Kara <jack@...e.cz>,
  kernel-dev@...lia.com
Subject: Re: [PATCH v6 1/9] fs: Create sb_encoding() helper

André Almeida <andrealmeid@...lia.com> writes:

> Filesystems that need to deal with the super block encoding need to use
> a if IS_ENABLED(CONFIG_UNICODE) around it because this struct member is
> not declared otherwise. In order to move this if/endif guards outside of
> the filesytem code and make it simpler, create a new function that
> returns the s_encoding member of struct super_block if Unicode is
> enabled, and return NULL otherwise.
>
> Suggested-by: Amir Goldstein <amir73il@...il.com>
> Reviewed-by: Amir Goldstein <amir73il@...il.com>
> Signed-off-by: André Almeida <andrealmeid@...lia.com>
> ---
>  include/linux/fs.h | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e1d4fef5c181d291a7c685e5897b2c018df439ae..a4d353a871b094b562a87ddcffe8336a26c5a3e2 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -3733,15 +3733,20 @@ static inline bool generic_ci_validate_strict_name(struct inode *dir, struct qst
>  }
>  #endif
>  
> -static inline bool sb_has_encoding(const struct super_block *sb)
> +static inline struct unicode_map *sb_encoding(const struct super_block *sb)
>  {
>  #if IS_ENABLED(CONFIG_UNICODE)
> -	return !!sb->s_encoding;
> +	return sb->s_encoding;
>  #else
> -	return false;
> +	return NULL;
>  #endif
>  }
>  
> +static inline bool sb_has_encoding(const struct super_block *sb)
> +{
> +	return !!sb_encoding(sb);
> +}
> +

FWIW, sb_has_encoding is completely superfluous now.  It is also only
used by overlayfs itself, so it should be easy to drop in favor of your
new helper in the following patches.  It even has a smaller function
name :)

>  int may_setattr(struct mnt_idmap *idmap, struct inode *inode,
>  		unsigned int ia_valid);
>  int setattr_prepare(struct mnt_idmap *, struct dentry *, struct iattr *);

-- 
Gabriel Krisman Bertazi