linux-kernel - Re: [PATCH] mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON

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Date:	Fri, 27 Dec 2013 17:19:44 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
CC:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON_PAGE

On 12/27/2013 05:38 AM, Kirill A. Shutemov wrote:
> On Thu, Dec 26, 2013 at 10:20:52PM -0500, Sasha Levin wrote:
>> Most of the VM_BUG_ON assertions are performed on a page. Usually, when
>> one of these assertions fails we'll get a BUG_ON with a call stack and
>> the registers.
>>
>> I've recently noticed based on the requests to add a small piece of code
>> that dumps the page to various VM_BUG_ON sites that the page dump is quite
>> useful to people debugging issues in mm.
>>
>> This patch adds a VM_BUG_ON_PAGE(cond, page) which beyond doing what
>> VM_BUG_ON() does, also dumps the page before executing the actual BUG_ON.
>>
>> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
>
> I like the idea. One thing I've noticed you have a lot of page flag based
> asserts, like:
>
> 	VM_BUG_ON_PAGE(PageLRU(page), page);
> 	VM_BUG_ON_PAGE(!PageLocked(page), page);
>
> What about adding per-page-flag assert macros, like:
>
> 	PageNotLRU_assert(page);
> 	PageLocked_assert(page);
>
> ? This way we will always dump right page on bug.
>

Sure, sounds good.

I'll send another patch on top of this one.


Thanks,
Sasha
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