linux-kernel - Re: [PATCH v1 4/4] mm/memory-failure: check __PG_HWPOISON separately from PAGE_FLAGS_CHECK_AT

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Date:	Thu, 23 Jul 2015 13:37:02 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Dean Nelson <dnelson@...hat.com>,
	"Tony Luck" <tony.luck@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	"Hugh Dickins" <hughd@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Naoya Horiguchi" <nao.horiguchi@...il.com>
Subject: Re: [PATCH v1 4/4] mm/memory-failure: check __PG_HWPOISON
 separately from PAGE_FLAGS_CHECK_AT_*

On Thu, 16 Jul 2015 01:41:56 +0000 Naoya Horiguchi <n-horiguchi@...jp.nec.com> wrote:

> The race condition addressed in commit add05cecef80 ("mm: soft-offline: don't
> free target page in successful page migration") was not closed completely,
> because that can happen not only for soft-offline, but also for hard-offline.
> Consider that a slab page is about to be freed into buddy pool, and then an
> uncorrected memory error hits the page just after entering __free_one_page(),
> then VM_BUG_ON_PAGE(page->flags & PAGE_FLAGS_CHECK_AT_PREP) is triggered,
> despite the fact that it's not necessary because the data on the affected
> page is not consumed.
> 
> To solve it, this patch drops __PG_HWPOISON from page flag checks at
> allocation/free time. I think it's justified because __PG_HWPOISON flags is
> defined to prevent the page from being reused and setting it outside the
> page's alloc-free cycle is a designed behavior (not a bug.)
> 
> And the patch reverts most of the changes from commit add05cecef80 about
> the new refcounting rule of soft-offlined pages, which is no longer necessary.
> 
> ...
>
> --- v4.2-rc2.orig/mm/memory-failure.c
> +++ v4.2-rc2/mm/memory-failure.c
> @@ -1723,6 +1723,9 @@ int soft_offline_page(struct page *page, int flags)
>  
>  	get_online_mems();
>  
> +	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
> +		set_migratetype_isolate(page, true);
> +
>  	ret = get_any_page(page, pfn, flags);
>  	put_online_mems();
>  	if (ret > 0) { /* for in-use pages */

This patch gets build-broken by your
mm-page_isolation-make-set-unset_migratetype_isolate-file-local.patch,
which I shall drop.

From: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: mm, page_isolation: make set/unset_migratetype_isolate() file-local

Nowaday, set/unset_migratetype_isolate() is defined and used only in
mm/page_isolation, so let's limit the scope within the file.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Minchan Kim <minchan@...nel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 include/linux/page-isolation.h |    5 -----
 mm/page_isolation.c            |    5 +++--
 2 files changed, 3 insertions(+), 7 deletions(-)

diff -puN include/linux/page-isolation.h~mm-page_isolation-make-set-unset_migratetype_isolate-file-local include/linux/page-isolation.h
--- a/include/linux/page-isolation.h~mm-page_isolation-make-set-unset_migratetype_isolate-file-local
+++ a/include/linux/page-isolation.h
@@ -65,11 +65,6 @@ undo_isolate_page_range(unsigned long st
 int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
 			bool skip_hwpoisoned_pages);
 
-/*
- * Internal functions. Changes pageblock's migrate type.
- */
-int set_migratetype_isolate(struct page *page, bool skip_hwpoisoned_pages);
-void unset_migratetype_isolate(struct page *page, unsigned migratetype);
 struct page *alloc_migrate_target(struct page *page, unsigned long private,
 				int **resultp);
 
diff -puN mm/page_isolation.c~mm-page_isolation-make-set-unset_migratetype_isolate-file-local mm/page_isolation.c
--- a/mm/page_isolation.c~mm-page_isolation-make-set-unset_migratetype_isolate-file-local
+++ a/mm/page_isolation.c
@@ -9,7 +9,8 @@
 #include <linux/hugetlb.h>
 #include "internal.h"
 
-int set_migratetype_isolate(struct page *page, bool skip_hwpoisoned_pages)
+static int set_migratetype_isolate(struct page *page,
+				bool skip_hwpoisoned_pages)
 {
 	struct zone *zone;
 	unsigned long flags, pfn;
@@ -72,7 +73,7 @@ out:
 	return ret;
 }
 
-void unset_migratetype_isolate(struct page *page, unsigned migratetype)
+static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
 {
 	struct zone *zone;
 	unsigned long flags, nr_pages;
_

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