linux-kernel - Re: [PATCH v2 01/13] mm: support madvise(MADV

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Message-ID: <20151104234055.GB7357@bbox>
Date:	Thu, 5 Nov 2015 08:40:55 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Michael Kerrisk <mtk.manpages@...il.com>,
	linux-api@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Jason Evans <je@...com>, Daniel Micay <danielmicay@...il.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Shaohua Li <shli@...nel.org>, Michal Hocko <mhocko@...e.cz>,
	yalin.wang2010@...il.com
Subject: Re: [PATCH v2 01/13] mm: support madvise(MADV_FREE)

On Wed, Nov 04, 2015 at 11:29:51AM +0900, Sergey Senozhatsky wrote:
> On (11/04/15 10:25), Minchan Kim wrote:
> [..]
> > +static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
> > +				unsigned long end, struct mm_walk *walk)
> > +
> > +{
> > +	struct mmu_gather *tlb = walk->private;
> > +	struct mm_struct *mm = tlb->mm;
> > +	struct vm_area_struct *vma = walk->vma;
> > +	spinlock_t *ptl;
> > +	pte_t *pte, ptent;
> > +	struct page *page;
> 
> 
> I'll just ask (probably I'm missing something)
> 
> 	+ pmd_trans_huge_lock() ?

No. It would be deadlock.

> 
> > +	split_huge_page_pmd(vma, addr, pmd);
> > +	if (pmd_trans_unstable(pmd))
> > +		return 0;
> > +
> > +	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
> > +	arch_enter_lazy_mmu_mode();
> > +	for (; addr != end; pte++, addr += PAGE_SIZE) {
> > +		ptent = *pte;
> > +
> > +		if (!pte_present(ptent))
> > +			continue;
> > +
> > +		page = vm_normal_page(vma, addr, ptent);
> > +		if (!page)
> > +			continue;
> > +
> 
> 	-ss
> 
> --
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