linux-kernel - Re: [PATCH 03/10] mm: Convert p[te|md]_numa users to p[te|md]_protnone

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Date:	Fri, 21 Nov 2014 10:58:34 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Mel Gorman <mgorman@...e.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Cc:	Linux-MM <linux-mm@...ck.org>,
	LinuxPPC-dev <linuxppc-dev@...ts.ozlabs.org>,
	Hugh Dickins <hughd@...gle.com>, Dave Jones <davej@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH 03/10] mm: Convert p[te|md]_numa users to p[te|md]_protnone_numa

Mel Gorman <mgorman@...e.de> writes:

> Convert existing users of pte_numa and friends to the new helper. Note
> that the kernel is broken after this patch is applied until the other
> page table modifiers are also altered. This patch layout is to make
> review easier.
>

.....

> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index c90e602..b5d58d3 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -173,7 +173,13 @@ void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
>  		pte_t pte)
>  {
>  #ifdef CONFIG_DEBUG_VM
> -	WARN_ON(pte_val(*ptep) & _PAGE_PRESENT);
> +	/*
> +	 * When handling numa faults, we already have the pte marked
> +	 * _PAGE_PRESENT, but we can be sure that it is not in hpte.
> +	 * Hence we can use set_pte_at for them.
> +	 */
> +	WARN_ON((pte_val(*ptep) & (_PAGE_PRESENT | _PAGE_USER)) ==
> +		(_PAGE_PRESENT | _PAGE_USER));
>  #endif


This can be VM_WARN_ON with #ifdef removed.

>  	/* Note: mm->context.id might not yet have been assigned as
>  	 * this context might not have been activated yet when this
> diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c

-aneesh

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