linux-kernel - Re: [Experimental][PATCH] putback_lru

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Date:	Fri, 20 Jun 2008 10:13:52 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Lee Schermerhorn <Lee.Schermerhorn@...com>
Cc:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	Kosaki Motohiro <kosaki.motohiro@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, kernel-testers@...r.kernel.org
Subject: Re: [Experimental][PATCH] putback_lru_page rework

Lee-san, this is an additonal one..
Not-tested-yet, just by review.

Fixing page_lock() <-> zone->lock nesting of bad-behavior.

Before:
      lock_page()(TestSetPageLocked())
      spin_lock(zone->lock)
      unlock_page()
      spin_unlock(zone->lock)  
After:
      spin_lock(zone->lock)
      spin_unlock(zone->lock)

Including nit-pick fix. (I'll ask Kosaki-san to merge this to his 5/5)

Hmm...

---
 mm/vmscan.c |   25 +++++--------------------
 1 file changed, 5 insertions(+), 20 deletions(-)

Index: test-2.6.26-rc5-mm3/mm/vmscan.c
===================================================================
--- test-2.6.26-rc5-mm3.orig/mm/vmscan.c
+++ test-2.6.26-rc5-mm3/mm/vmscan.c
@@ -1106,7 +1106,7 @@ static unsigned long shrink_inactive_lis
 		if (nr_taken == 0)
 			goto done;
 
-		spin_lock(&zone->lru_lock);
+		spin_lock_irq(&zone->lru_lock);
 		/*
 		 * Put back any unfreeable pages.
 		 */
@@ -1136,9 +1136,8 @@ static unsigned long shrink_inactive_lis
 			}
 		}
   	} while (nr_scanned < max_scan);
-	spin_unlock(&zone->lru_lock);
+	spin_unlock_irq(&zone->lru_lock);
 done:
-	local_irq_enable();
 	pagevec_release(&pvec);
 	return nr_reclaimed;
 }
@@ -2438,7 +2437,7 @@ static void show_page_path(struct page *
  */
 static void check_move_unevictable_page(struct page *page, struct zone *zone)
 {
-
+retry:
 	ClearPageUnevictable(page); /* for page_evictable() */
 	if (page_evictable(page, NULL)) {
 		enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page);
@@ -2455,6 +2454,8 @@ static void check_move_unevictable_page(
 		 */
 		SetPageUnevictable(page);
 		list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list);
+		if (page_evictable(page, NULL))
+			goto retry;
 	}
 }
 
@@ -2494,16 +2495,6 @@ void scan_mapping_unevictable_pages(stru
 				next = page_index;
 			next++;
 
-			if (TestSetPageLocked(page)) {
-				/*
-				 * OK, let's do it the hard way...
-				 */
-				if (zone)
-					spin_unlock_irq(&zone->lru_lock);
-				zone = NULL;
-				lock_page(page);
-			}
-
 			if (pagezone != zone) {
 				if (zone)
 					spin_unlock_irq(&zone->lru_lock);
@@ -2514,8 +2505,6 @@ void scan_mapping_unevictable_pages(stru
 			if (PageLRU(page) && PageUnevictable(page))
 				check_move_unevictable_page(page, zone);
 
-			unlock_page(page);
-
 		}
 		if (zone)
 			spin_unlock_irq(&zone->lru_lock);
@@ -2551,15 +2540,11 @@ void scan_zone_unevictable_pages(struct 
 		for (scan = 0;  scan < batch_size; scan++) {
 			struct page *page = lru_to_page(l_unevictable);
 
-			if (TestSetPageLocked(page))
-				continue;
-
 			prefetchw_prev_lru_page(page, l_unevictable, flags);
 
 			if (likely(PageLRU(page) && PageUnevictable(page)))
 				check_move_unevictable_page(page, zone);
 
-			unlock_page(page);
 		}
 		spin_unlock_irq(&zone->lru_lock);
 

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