linux-kernel - Re: [PATCH v2] Add FAT messages to printk index

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Date:   Thu, 24 Mar 2022 14:45:22 +0900
From:   OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:     Jonathan Lassoff <jof@...jof.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] Add FAT messages to printk index

Jonathan Lassoff <jof@...jof.com> writes:

> In order for end users to quickly react to new issues that come up in
> production, it is proving useful to leverage the printk indexing system. This
> printk index enables kernel developers to use calls to printk() with changable
> ad-hoc format strings, while still enabling end users to detect changes and
> develop a semi-stable interface for detecting and parsing these messages.
>
> So that detailed FAT messages are captured by this printk index, this patch
> wraps fat_msg with a macro.
>
> PATCH v1 -- Fix indentation with tabs in fat_msg macro
> PATCH v2 -- Define FAT_PRINTK_PREFIX
> PATCH v3 -- Fix kernel-doc comment for _fat_msg()
>
> Reported-by: kernel test robot <lkp@...el.com>

Acked-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>

Thanks.

> ---
>  fs/fat/fat.h  |  9 ++++++++-
>  fs/fat/misc.c | 14 ++++++++++----
>  2 files changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fat/fat.h b/fs/fat/fat.h
> index 02d4d4234956..2a20a21f2fb9 100644
> --- a/fs/fat/fat.h
> +++ b/fs/fat/fat.h
> @@ -433,8 +433,15 @@ void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...);
>  	__fat_fs_error(sb, 1, fmt , ## args)
>  #define fat_fs_error_ratelimit(sb, fmt, args...) \
>  	__fat_fs_error(sb, __ratelimit(&MSDOS_SB(sb)->ratelimit), fmt , ## args)
> +
> +#define FAT_PRINTK_PREFIX "%sFAT-fs (%s): "
> +#define fat_msg(sb, level, fmt, args...)				\
> +do {									\
> +	printk_index_subsys_emit(FAT_PRINTK_PREFIX, level, fmt, ##args);\
> +	_fat_msg(sb, level, fmt, ##args);				\
> +} while(0)
>  __printf(3, 4) __cold
> -void fat_msg(struct super_block *sb, const char *level, const char *fmt, ...);
> +void _fat_msg(struct super_block *sb, const char *level, const char *fmt, ...);
>  #define fat_msg_ratelimit(sb, level, fmt, args...)	\
>  	do {	\
>  			if (__ratelimit(&MSDOS_SB(sb)->ratelimit))	\
> diff --git a/fs/fat/misc.c b/fs/fat/misc.c
> index 91ca3c304211..855477d89f41 100644
> --- a/fs/fat/misc.c
> +++ b/fs/fat/misc.c
> @@ -42,10 +42,16 @@ void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...)
>  EXPORT_SYMBOL_GPL(__fat_fs_error);
>  
>  /**
> - * fat_msg() - print preformated FAT specific messages. Every thing what is
> - * not fat_fs_error() should be fat_msg().
> + * _fat_msg() - Print a preformatted FAT message based on a superblock.
> + * @sb: A pointer to a &struct super_block
> + * @level: A Kernel printk level constant
> + * @fmt: The printf-style format string to print.
> + *
> + * Everything that is not fat_fs_error() should be fat_msg().
> + *
> + * fat_msg() wraps _fat_msg() for printk indexing.
>   */
> -void fat_msg(struct super_block *sb, const char *level, const char *fmt, ...)
> +void _fat_msg(struct super_block *sb, const char *level, const char *fmt, ...)
>  {
>  	struct va_format vaf;
>  	va_list args;
> @@ -53,7 +59,7 @@ void fat_msg(struct super_block *sb, const char *level, const char *fmt, ...)
>  	va_start(args, fmt);
>  	vaf.fmt = fmt;
>  	vaf.va = &args;
> -	printk("%sFAT-fs (%s): %pV\n", level, sb->s_id, &vaf);
> +	_printk(FAT_PRINTK_PREFIX "%pV\n", level, sb->s_id, &vaf);
>  	va_end(args);
>  }

-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>