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

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Date:	Tue, 02 Dec 2014 13:01:29 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Mel Gorman <mgorman@...e.de>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	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>,
	Paul Mackerras <paulus@...ba.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 03/10] mm: Convert p[te|md]_numa users to p[te|md]_protnone_numa

Benjamin Herrenschmidt <benh@...nel.crashing.org> writes:

> On Fri, 2014-11-21 at 13:57 +0000, Mel Gorman wrote:
>> 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);
>> -#endif
>> +       /*
>> +        * 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.
>> +        */
>> +       VM_WARN_ON((pte_val(*ptep) & (_PAGE_PRESENT | _PAGE_USER)) ==
>> +               (_PAGE_PRESENT | _PAGE_USER));
>> +
>
> His is that going to fare with set_pte_at() called for kernel pages ?
>

Yes, we won't capture those errors now. But is there any other debug
check i could use to capture the wrong usage of set_pte_at ?

-aneesh

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