linux-kernel - Re: [PATCH -mm v2] mm: add page_check_address

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Date:	Tue, 24 Nov 2015 11:09:30 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	Vladimir Davydov <vdavydov@...tuozzo.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm v2] mm: add page_check_address_transhuge helper

On Tue, Nov 24, 2015 at 01:29:41PM +0900, Sergey Senozhatsky wrote:
> Hello,
> 
> On (11/20/15 12:31), Vladimir Davydov wrote:
> [..]
> > -	if (ptep_clear_flush_young_notify(vma, address, pte)) {
> > -		/*
> > -		 * Don't treat a reference through a sequentially read
> > -		 * mapping as such.  If the page has been used in
> > -		 * another mapping, we will catch it; if this other
> > -		 * mapping is already gone, the unmap path will have
> > -		 * set PG_referenced or activated the page.
> > -		 */
> > -		if (likely(!(vma->vm_flags & VM_SEQ_READ)))
> > +	if (pte) {
> > +		if (ptep_clear_flush_young_notify(vma, address, pte)) {
> > +			/*
> > +			 * Don't treat a reference through a sequentially read
> > +			 * mapping as such.  If the page has been used in
> > +			 * another mapping, we will catch it; if this other
> > +			 * mapping is already gone, the unmap path will have
> > +			 * set PG_referenced or activated the page.
> > +			 */
> > +			if (likely(!(vma->vm_flags & VM_SEQ_READ)))
> > +				referenced++;
> > +		}
> > +		pte_unmap(pte);
> > +	} else {
> > +		if (pmdp_clear_flush_young_notify(vma, address, pmd))
> >  			referenced++;
> >  	}
> 
> # CONFIG_TRANSPARENT_HUGEPAGE is not set
> 
> x86_64, 4.4.0-rc2-mm1
> 
> 
> mm/built-in.o: In function `page_referenced_one':
> rmap.c:(.text+0x32070): undefined reference to `pmdp_clear_flush_young'

Something like this?

diff --git a/mm/page_idle.c b/mm/page_idle.c
index 374931f32ebc..4ea9c4ef5146 100644
--- a/mm/page_idle.c
+++ b/mm/page_idle.c
@@ -66,8 +66,12 @@ static int page_idle_clear_pte_refs_one(struct page *page,
 	if (pte) {
 		referenced = ptep_clear_young_notify(vma, addr, pte);
 		pte_unmap(pte);
-	} else
+	} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
 		referenced = pmdp_clear_young_notify(vma, addr, pmd);
+	} else {
+		/* unexpected pmd-mapped page? */
+		WARN_ON_ONCE(1);
+	}
 
 	spin_unlock(ptl);
 
diff --git a/mm/rmap.c b/mm/rmap.c
index 27916086ac50..499b24511b1f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -929,9 +929,12 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
 				referenced++;
 		}
 		pte_unmap(pte);
-	} else {
+	} else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
 		if (pmdp_clear_flush_young_notify(vma, address, pmd))
 			referenced++;
+	} else {
+		/* unexpected pmd-mapped page? */
+		WARN_ON_ONCE(1);
 	}
 	spin_unlock(ptl);
 
-- 
 Kirill A. Shutemov
--
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