Re: [PATCH] ext4: Reduce object size of ext4_msg uses

On Fri, Jul 24, 2026 at 06:23:36PM -0700, Joe Perches wrote:
> Reduce the object size of ext4 ~2KB (~.5%) by combining the KERN_<LEVEL>
> and format uses of ext4_msg.
> 
> Separate them in __ext4_msg using printk_get_level and printk_skip_level
> and emitting the appropriate level.
> 
> x86 object sizes before and after:
> 
> defconfig size before:
> $ size -t fs/ext4/built-in.a | tail -1
>  579013	 121634	    316	 700963	  ab223	(TOTALS)
> 
> defconfig size after:
> $ size -t fs/ext4/built-in.a | tail -1
>  577196	 121650	    316	 699162	  aab1a	(TOTALS)
> 
> defconfig size before with CONFIG_EXPERT=y and CONFIG_PRINTK=n:
> $ size -t fs/ext4/built-in.a | tail -1
>  537999	 121432	    316	 659747	  a1123	(TOTALS)
> 
> defconfig size after with CONFIG_EXPERT=y and CONFIG_PRINTK=n:
> $ size -t fs/ext4/built-in.a | tail -1
>  536837	 121424	    316	 658577	  a0c91	(TOTALS)
> 
> Signed-off-by: Joe Perches <[email protected]>

Interesting, on powerpc64, we save around 1 - 2K. Its not much but sure,
maybe some embedded or chip bringup scenarios might find it useful.

Reviewed-by: Ojaswin Mujoo <[email protected]>

Regards,
ojaswin

> ---
>  fs/ext4/ext4.h  | 12 ++++++------
>  fs/ext4/super.c | 14 +++++++++-----
>  2 files changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index b37c136ea3ab..981918f32067 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -3309,8 +3309,8 @@ void __ext4_warning(struct super_block *, const char *, unsigned int,
>  extern __printf(4, 5)
>  void __ext4_warning_inode(const struct inode *inode, const char *function,
>  			  unsigned int line, const char *fmt, ...);
> -extern __printf(3, 4)
> -void __ext4_msg(struct super_block *, const char *, const char *, ...);
> +extern __printf(2, 3)
> +void __ext4_msg(struct super_block *, const char *fmt, ...);
>  extern void __dump_mmp_msg(struct super_block *, struct mmp_struct *mmp,
>  			   const char *, unsigned int, const char *);
>  extern __printf(7, 8)
> @@ -3354,8 +3354,8 @@ void __ext4_grp_locked_error(const char *, unsigned int,
>  	__ext4_warning(sb, __func__, __LINE__, fmt, ##__VA_ARGS__)
>  #define ext4_warning_inode(inode, fmt, ...)				\
>  	__ext4_warning_inode(inode, __func__, __LINE__, fmt, ##__VA_ARGS__)
> -#define ext4_msg(sb, level, fmt, ...)				\
> -	__ext4_msg(sb, level, fmt, ##__VA_ARGS__)
> +#define ext4_msg(sb, level, fmt, ...)					\
> +	__ext4_msg(sb, level fmt, ##__VA_ARGS__)
>  #define dump_mmp_msg(sb, mmp, msg)					\
>  	__dump_mmp_msg(sb, mmp, __func__, __LINE__, msg)
>  #define ext4_grp_locked_error(sb, grp, ino, block, fmt, ...)		\
> @@ -3401,8 +3401,8 @@ do {									\
>  } while (0)
>  #define ext4_msg(sb, level, fmt, ...)					\
>  do {									\
> -	no_printk(fmt, ##__VA_ARGS__);					\
> -	__ext4_msg(sb, "", " ");					\
> +	no_printk(level fmt, ##__VA_ARGS__);				\
> +	__ext4_msg(sb, "" " ");						\
>  } while (0)
>  #define dump_mmp_msg(sb, mmp, msg)					\
>  	__dump_mmp_msg(sb, mmp, "", 0, "")
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 245f67d10ded..72d6f6353a27 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -981,11 +981,11 @@ void __ext4_std_error(struct super_block *sb, const char *function,
>  	ext4_handle_error(sb, false, -errno, 0, 0, function, line);
>  }
>  
> -void __ext4_msg(struct super_block *sb,
> -		const char *prefix, const char *fmt, ...)
> +void __ext4_msg(struct super_block *sb, const char *fmt, ...)
>  {
>  	struct va_format vaf;
>  	va_list args;
> +	int level;
>  
>  	if (sb) {
>  		atomic_inc(&EXT4_SB(sb)->s_msg_count);
> @@ -995,12 +995,16 @@ void __ext4_msg(struct super_block *sb,
>  	}
>  
>  	va_start(args, fmt);
> -	vaf.fmt = fmt;
> +
> +	level = printk_get_level(fmt);
> +	vaf.fmt = printk_skip_level(fmt);
>  	vaf.va = &args;
>  	if (sb)
> -		printk("%sEXT4-fs (%s): %pV\n", prefix, sb->s_id, &vaf);
> +		printk("%c%cEXT4-fs (%s): %pV\n",
> +		       KERN_SOH_ASCII, level, sb->s_id, &vaf);
>  	else
> -		printk("%sEXT4-fs: %pV\n", prefix, &vaf);
> +		printk("%c%cEXT4-fs: %pV\n",
> +		       KERN_SOH_ASCII, level, &vaf);
>  	va_end(args);
>  }
>