linux-kernel - Re: [PATCH 1/3] Add ratelimited printk for different alert levels

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Date:	Wed, 12 Sep 2012 08:43:37 +1000
From:	Dave Chinner <david@...morbit.com>
To:	raghu.prabhu13@...il.com
Cc:	xfs@....sgi.com, Raghavendra D Prabhu <rprabhu@...hang.net>,
	Ben Myers <bpm@....com>, Alex Elder <elder@...nel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] Add ratelimited printk for different alert levels

On Wed, Sep 12, 2012 at 03:43:22AM +0530, raghu.prabhu13@...il.com wrote:
> From: Raghavendra D Prabhu <rprabhu@...hang.net>
> 
> Ratelimited printk will be useful in printing xfs messages which are otherwise
> not required to be printed always due to their high rate (to prevent kernel ring
> buffer from overflowing), while at the same time required to be printed.
> 
> Signed-off-by: Raghavendra D Prabhu <rprabhu@...hang.net>
> ---
>  fs/xfs/xfs_message.h | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/fs/xfs/xfs_message.h b/fs/xfs/xfs_message.h
> index 56dc0c1..87999a5 100644
> --- a/fs/xfs/xfs_message.h
> +++ b/fs/xfs/xfs_message.h
> @@ -1,6 +1,8 @@
>  #ifndef __XFS_MESSAGE_H
>  #define __XFS_MESSAGE_H 1
>  
> +#include <linux/ratelimit.h>
> +

Include this in xfs_linux.h rather than here.

>  struct xfs_mount;
>  
>  extern __printf(2, 3)
> @@ -30,6 +32,32 @@ void xfs_debug(const struct xfs_mount *mp, const char *fmt, ...)
>  }
>  #endif
>  
> +#define xfs_printk_ratelimited(xfs_printk, dev, fmt, ...)		\
> +do {									\
> +	static DEFINE_RATELIMIT_STATE(_rs,				\
> +				      DEFAULT_RATELIMIT_INTERVAL,	\
> +				      DEFAULT_RATELIMIT_BURST);		\
> +	if (__ratelimit(&_rs))						\
> +		xfs_printk(dev, fmt, ##__VA_ARGS__);			\
> +} while (0)

Use "func" not xfs_printk here. xfs_printk looks too much like a
real function name (indeed, we already have __xfs_printk) rather
than a macro parameter.

> +#define xfs_emerg_ratelimited(dev, fmt, ...)				\
> +	xfs_printk_ratelimited(xfs_emerg, dev, fmt, ##__VA_ARGS__)
> +#define xfs_alert_ratelimited(dev, fmt, ...)				\
> +	xfs_printk_ratelimited(xfs_alert, dev, fmt, ##__VA_ARGS__)
> +#define xfs_crit_ratelimited(dev, fmt, ...)				\
> +	xfs_printk_ratelimited(xfs_crit, dev, fmt, ##__VA_ARGS__)
> +#define xfs_err_ratelimited(dev, fmt, ...)				\
> +	xfs_printk_ratelimited(xfs_err, dev, fmt, ##__VA_ARGS__)
> +#define xfs_warn_ratelimited(dev, fmt, ...)				\
> +	xfs_printk_ratelimited(xfs_warn, dev, fmt, ##__VA_ARGS__)
> +#define xfs_notice_ratelimited(dev, fmt, ...)				\
> +	xfs_printk_ratelimited(xfs_notice, dev, fmt, ##__VA_ARGS__)
> +#define xfs_info_ratelimited(dev, fmt, ...)				\
> +	xfs_printk_ratelimited(xfs_info, dev, fmt, ##__VA_ARGS__)
> +#define xfs_dbg_ratelimited(dev, fmt, ...)				\
> +	xfs_printk_ratelimited(xfs_dbg, dev, fmt, ##__VA_ARGS__)

Here's the problem with adding macros that aren't used. xfs_dbg
does not exist - the function is xfs_debug(). The compiler won't
catch that until the macro is used, so only add the macros which are
needed for this patch series.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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