linux-kernel - [PATCH] memory unplug v7 [2/6]

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Message-Id: <20070706182420.d7d3b615.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 6 Jul 2007 18:24:20 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <clameter@....com>, mel@....ul.ie
Subject: [PATCH] memory unplug v7 [2/6] - isolate_lru_page fix

release_pages() in mm/swap.c changes page_count() to be 0
without removing PageLRU flag...

This means isolate_lru_page() can see a page, PageLRU() && page_count(page)==0..
This is BUG. (get_page() will be called against count=0 page.)

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

---
 mm/migrate.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Index: linux-2.6.22-rc6-mm1/mm/migrate.c
===================================================================
--- linux-2.6.22-rc6-mm1.orig/mm/migrate.c
+++ linux-2.6.22-rc6-mm1/mm/migrate.c
@@ -49,9 +49,8 @@ int isolate_lru_page(struct page *page, 
 		struct zone *zone = page_zone(page);
 
 		spin_lock_irq(&zone->lru_lock);
-		if (PageLRU(page)) {
+		if (PageLRU(page) && get_page_unless_zero(page)) {
 			ret = 0;
-			get_page(page);
 			ClearPageLRU(page);
 			if (PageActive(page))
 				del_page_from_active_list(zone, page);

-
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