From: Mel Gorman <mgorman@suse.de>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>, Hugh Dickins <hughd@google.com>,
Dave Jones <davej@redhat.com>, Rik van Riel <riel@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Kirill Shutemov <kirill.shutemov@linux.intel.com>,
Sasha Levin <sasha.levin@oracle.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [RFC PATCH 0/7] Replace _PAGE_NUMA with PAGE_NONE protections
Date: Tue, 18 Nov 2014 17:08:25 +0000 [thread overview]
Message-ID: <20141118170825.GD2725@suse.de> (raw)
In-Reply-To: <87y4r879k5.fsf@linux.vnet.ibm.com>
On Tue, Nov 18, 2014 at 10:03:30PM +0530, Aneesh Kumar K.V wrote:
> > diff --git a/arch/powerpc/mm/copro_fault.c b/arch/powerpc/mm/copro_fault.c
> > index 5a236f0..46152aa 100644
> > --- a/arch/powerpc/mm/copro_fault.c
> > +++ b/arch/powerpc/mm/copro_fault.c
> > @@ -64,7 +64,12 @@ int copro_handle_mm_fault(struct mm_struct *mm, unsigned long ea,
> > if (!(vma->vm_flags & VM_WRITE))
> > goto out_unlock;
> > } else {
> > - if (dsisr & DSISR_PROTFAULT)
> > + /*
> > + * protfault should only happen due to us
> > + * mapping a region readonly temporarily. PROT_NONE
> > + * is also covered by the VMA check above.
> > + */
> > + if (WARN_ON_ONCE(dsisr & DSISR_PROTFAULT))
> > goto out_unlock;
> > if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
> > goto out_unlock;
>
>
> we should do that DSISR_PROTFAILT check after vma->vm_flags. It is not
> that we will not hit DSISR_PROTFAULT, what we want to ensure here is that
> we get a prot fault only for cases convered by that vma check. So
> everything should be taking the if (!(vma->vm_flags & (VM_READ |
> VM_EXEC))) branch if it is a protfault. If not we would like to know
> about that. And hence the idea of not using WARN_ON_ONCE. I was also not
> sure whether we want to enable that always. The reason for keeping that
> within CONFIG_DEBUG_VM is to make sure that nobody ends up depending on
> PROTFAULT outside the vma check convered. So expectations is that
> developers working on feature will run with DEBUG_VM enable and finds
> this warning. We don't expect to hit this otherwise.
>
/me slaps self. It's clear now and updated accordingly. Thanks.
--
Mel Gorman
SUSE Labs
prev parent reply other threads:[~2014-11-18 17:08 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-14 13:32 [RFC PATCH 0/7] Replace _PAGE_NUMA with PAGE_NONE protections Mel Gorman
2014-11-14 13:33 ` [PATCH 1/7] mm: Add p[te|md] protnone helpers for use by NUMA balancing Mel Gorman
2014-11-14 13:33 ` [PATCH 2/7] mm: Convert p[te|md]_numa users to p[te|md]_protnone_numa Mel Gorman
2014-11-14 13:33 ` [PATCH 3/7] mm: Convert p[te|md]_mknonnuma and remaining page table manipulations Mel Gorman
2014-11-14 13:33 ` [PATCH 4/7] mm: Remove remaining references to NUMA hinting bits and helpers Mel Gorman
2014-11-14 13:33 ` [PATCH 5/7] mm: numa: Do not trap faults on the huge zero page Mel Gorman
2014-11-14 13:33 ` [PATCH 6/7] x86: mm: Restore original pte_special check Mel Gorman
2014-11-14 13:33 ` [PATCH 7/7] mm: numa: Add paranoid check around pte_protnone_numa Mel Gorman
2014-11-15 1:41 ` [RFC PATCH 0/7] Replace _PAGE_NUMA with PAGE_NONE protections Linus Torvalds
2014-11-15 3:29 ` Sasha Levin
2014-11-18 15:42 ` Mel Gorman
2014-11-18 16:33 ` Sasha Levin
2014-11-18 16:56 ` Aneesh Kumar K.V
2014-11-18 17:14 ` Mel Gorman
2014-11-18 17:18 ` Sasha Levin
2014-11-19 13:14 ` Mel Gorman
2014-11-17 8:26 ` Aneesh Kumar K.V
2014-11-18 16:01 ` Mel Gorman
2014-11-18 16:33 ` Aneesh Kumar K.V
2014-11-18 17:08 ` Mel Gorman [this message]
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