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From: Neil Brown <neilb@cse.unsw.edu.au>
To: Benjamin LaHaise <bcrl@redhat.com>
Date: Wed, 9 Oct 2002 09:31:14 +1000
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Message-ID: <15779.27330.284336.914423@notabene.cse.unsw.edu.au>
Cc: mingo@redhat.com, Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [patch] silence an unnescessary raid5 debugging message
In-Reply-To: message from Benjamin LaHaise on Tuesday October 8
References: <20021008180350.A15858@redhat.com>
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On Tuesday October 8, bcrl@redhat.com wrote:
> Hello Ingo,
> 
> LVM manages to trigger the "raid5: switching cache buffer size" printk 
> quiet voluminously when using a snapshot device.  The following patch 
> disables it by placing it under the debugging PRINTK macro.

This is there as a 'printk' deliberately.  It warns you that what you
are doing isn't really supported and will cause a substantial
performance hit (as all IO to the array is completely serialised
around one of these messages).

If you want to make it PRITNK for yourself, that is fine.  But I would
rather it stayed as printk in the mainstream kernel untill the root
problem is fixed (and I have seen patches that possibly fix the
problem, but I haven't had a chance to look at them).

NeilBrown

> 
> 		-ben
> -- 
> "Do you seek knowledge in time travel?"
> 
> diff -urN linux.orig/drivers/md/raid5.c linux/drivers/md/raid5.c
> --- linux.orig/drivers/md/raid5.c	Mon Feb 25 14:37:58 2002
> +++ linux/drivers/md/raid5.c	Tue Oct  8 17:56:43 2002
> @@ -282,7 +282,7 @@
>  				}
>  
>  				if (conf->buffer_size != size) {
> -					printk("raid5: switching cache buffer size, %d --> %d\n", oldsize, size);
> +					PRINTK("raid5: switching cache buffer size, %d --> %d\n", oldsize, size);
>  					shrink_stripe_cache(conf);
>  					if (size==0) BUG();
>  					conf->buffer_size = size;
> -
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