Subject: Re: [RFC PATCH powerpc] try secondary hash before BUG in kernel_map_linear_page()

From: Li Zhong <[email-masked]>
Date: Wed, 10 Apr 2013 13:29:19 +0800

On Wed, 2013-04-10 at 12:21 +1000, Michael Ellerman wrote:
> On Mon, Feb 25, 2013 at 05:29:35PM +0800, Li Zhong wrote:
> > This patch tries to fix following issue when CONFIG_DEBUG_PAGEALLOC
> > is enabled:
> > 
> > [  543.075675] ------------[ cut here ]------------
> > [  543.075701] kernel BUG at arch/powerpc/mm/hash_utils_64.c:1239!
> > [  543.075714] Oops: Exception in kernel mode, sig: 5 [#1]

Hi Michael, 

Thanks for the review.

> So the issue is that kernel_map_linear_page() doesn't try the secondary
> hash slot.

It seems so.

> > The code is borrowed from that in __hash_page_huge().
> 
> It is, and in fact there is another copy in hash_low_64.S - in assembler.
> 
> So I think we should at least try and keep ourselves to two
> implementations, one in asm and one in C. So can you split it out into a
> helper routine called by both kernel_map_linear_page() and
> __hash_page_huge() ?

OK, I'll try to update it as you suggested. 

Thanks, Zhong

> cheers