linux-kernel - Re: [PATCH 6/9] mm/page_alloc: add informative debugging message in page_outside_zone

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Message-ID: <5111859B.7060004@linux.vnet.ibm.com>
Date:	Tue, 05 Feb 2013 14:20:11 -0800
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Linux MM <linux-mm@...ck.org>,
	David Hansen <dave@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH 6/9] mm/page_alloc: add informative debugging message
 in page_outside_zone_boundaries()

On 02/01/2013 04:29 PM, Andrew Morton wrote:
> On Fri, 1 Feb 2013 16:28:48 -0800
> Andrew Morton <akpm@...ux-foundation.org> wrote:
>
>>> +	if (ret)
>>> +		pr_debug("page %lu outside zone [ %lu - %lu ]\n",
>>> +			pfn, start_pfn, start_pfn + sp);
>>> +
>>>   	return ret;
>>>   }
>>
>> As this condition leads to a VM_BUG_ON(), "pr_debug" seems rather wimpy
>> and I doubt if we need to be concerned about flooding the console.
>>
>> I'll switch it to pr_err.
>
> otoh, as nobody has ever hit that VM_BUG_ON() (yes?), do we really need
> the patch?

I've hit this bug while developing some code that moves pages between zones.

As it helped me debug that issue with my own code, I could see how 
another developer might be helped by it.

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