linux-kernel - Re: [PATCH 3/4] exfat: Expand exfat_err() and co directly to pr

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Date:   Sat, 23 Jul 2022 10:04:09 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Joe Perches <joe@...ches.com>
Cc:     linux-fsdevel@...r.kernel.org, Namjae Jeon <linkinjeon@...nel.org>,
        Sungjong Seo <sj1557.seo@...sung.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] exfat: Expand exfat_err() and co directly to pr_*() macro

On Sat, 23 Jul 2022 09:42:12 +0200,
Joe Perches wrote:
> 
> On Fri, 2022-07-22 at 16:29 +0200, Takashi Iwai wrote:
> > Currently the error and info messages handled by exfat_err() and co
> > are tossed to exfat_msg() function that does nothing but passes the
> > strings with printk() invocation.  Not only that this is more overhead
> > by the indirect calls, but also this makes harder to extend for the
> > debug print usage; because of the direct printk() call, you cannot
> > make it for dynamic debug or without debug like the standard helpers
> > such as pr_debug() or dev_dbg().
> > 
> > For addressing the problem, this patch replaces exfat_msg() function
> > with a macro to expand to pr_*() directly.  This allows us to create
> > exfat_debug() macro that is expanded to pr_debug() (which output can
> > gracefully suppressed via dyndbg).
> []
> > diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
> []
> > @@ -508,14 +508,19 @@ void __exfat_fs_error(struct super_block *sb, int report, const char *fmt, ...)
> >  #define exfat_fs_error_ratelimit(sb, fmt, args...) \
> >  		__exfat_fs_error(sb, __ratelimit(&EXFAT_SB(sb)->ratelimit), \
> >  		fmt, ## args)
> > -void exfat_msg(struct super_block *sb, const char *lv, const char *fmt, ...)
> > -		__printf(3, 4) __cold;
> > +
> > +/* expand to pr_xxx() with prefix */
> > +#define exfat_msg(sb, lv, fmt, ...) \
> > +	pr_##lv("exFAT-fs (%s): " fmt "\n", (sb)->s_id, ##__VA_ARGS__)
> > +
> >  #define exfat_err(sb, fmt, ...)						\
> > -	exfat_msg(sb, KERN_ERR, fmt, ##__VA_ARGS__)
> > +	exfat_msg(sb, err, fmt, ##__VA_ARGS__)
> >  #define exfat_warn(sb, fmt, ...)					\
> > -	exfat_msg(sb, KERN_WARNING, fmt, ##__VA_ARGS__)
> > +	exfat_msg(sb, warn, fmt, ##__VA_ARGS__)
> >  #define exfat_info(sb, fmt, ...)					\
> > -	exfat_msg(sb, KERN_INFO, fmt, ##__VA_ARGS__)
> > +	exfat_msg(sb, info, fmt, ##__VA_ARGS__)
> > +#define exfat_debug(sb, fmt, ...)					\
> > +	exfat_msg(sb, debug, fmt, ##__VA_ARGS__)
> 
> I think this would be clearer using pr_<level> directly instead
> of an indirecting macro that uses concatenation of <level> that
> obscures the actual use of pr_<level>
> 
> Either: (and this first option would be my preference)
> 
> #define exfat_err(sb, fmt, ...) \
> 	pr_err("exFAT-fs (%s): " fmt "\n", (sb)->s_id, ##__VA_ARGS__)
> #define exfat_warn(sb, fmt, ...) \
> 	pr_warn("exFAT-fs (%s): " fmt "\n", (sb)->s_id, ##__VA_ARGS__)
> etc...

IMO, it's a matter of taste, and I don't mind either way.
Just let me know.

> or using an indirecting macro:
> 
> #define exfat_printk(pr_level, sb, fmt, ...)	\
> 	pr_level("exFAT-fs (%s): " fmt "\n", (sb)->s_id, ##__VA_ARGS__)

Is pr_level() defined anywhere...?

> 
> and btw, there are multiple uses of exfat_<level> output with a
> unnecessary and duplicated '\n' that the macro already adds that
> should be removed:
> 
> $ git grep -P -n '\bexfat_(err|warn|info).*\\n' fs/exfat/
> fs/exfat/fatent.c:334:                  exfat_err(sb, "sbi->clu_srch_ptr is invalid (%u)\n",
> fs/exfat/nls.c:674:                     exfat_err(sb, "failed to read sector(0x%llx)\n",
> fs/exfat/super.c:467:           exfat_err(sb, "bogus sector size bits : %u\n",
> fs/exfat/super.c:476:           exfat_err(sb, "bogus sectors bits per cluster : %u\n",

Right, that should be addressed in another patch.


thanks,

Takashi