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From: Minchan Kim <minchan@kernel.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, Jason Evans <je@fb.com>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Will Deacon <will.deacon@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	"[4.5+]" <stable@vger.kernel.org>,
	Andreas Schwab <schwab@suse.de>
Subject: Re: [PATCH] mm: pmd dirty emulation in page fault handler
Date: Thu, 22 Dec 2016 23:52:03 +0900	[thread overview]
Message-ID: <20161222145203.GA18970@bbox> (raw)
In-Reply-To: <20161222081713.GA32480@node.shutemov.name>

Hello,

On Thu, Dec 22, 2016 at 11:17:13AM +0300, Kirill A. Shutemov wrote:

< snip >
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 36c774f..7408ddc 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -3637,18 +3637,20 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> >  			if (pmd_protnone(orig_pmd) && vma_is_accessible(vma))
> >  				return do_huge_pmd_numa_page(&vmf, orig_pmd);
> >  
> > -			if ((vmf.flags & FAULT_FLAG_WRITE) &&
> > -					!pmd_write(orig_pmd)) {
> > -				ret = wp_huge_pmd(&vmf, orig_pmd);
> > -				if (!(ret & VM_FAULT_FALLBACK))
> > +			if (vmf.flags & FAULT_FLAG_WRITE) {
> > +				if (!pmd_write(orig_pmd)) {
> > +					ret = wp_huge_pmd(&vmf, orig_pmd);
> > +					if (ret == VM_FAULT_FALLBACK)
> 
> In theory, more than one flag can be set and it would lead to
> false-negative. Bit check was the right thing.
> 
> And I don't understand why do you need to change code in
> __handle_mm_fault() at all.
> From what I see change to huge_pmd_set_accessed() should be enough.

Yeb. Thanks for the review. Here v2 goes.

  reply	other threads:[~2016-12-22 14:52 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-21 23:48 [PATCH] mm: pmd dirty emulation in page fault handler Minchan Kim
2016-12-22  8:17 ` Kirill A. Shutemov
2016-12-22 14:52   ` Minchan Kim [this message]
2016-12-22 18:35     ` Kirill A. Shutemov
2016-12-22 22:12     ` Andreas Schwab
2016-12-23  9:17     ` Michal Hocko
2016-12-23  9:53       ` Minchan Kim
2016-12-23 11:54         ` Michal Hocko
2016-12-23 14:01           ` Minchan Kim
2016-12-23 14:53             ` Michal Hocko

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