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Commit 58c37f6e authored by KOSAKI Motohiro's avatar KOSAKI Motohiro Committed by Linus Torvalds
Browse files

vmscan: protect reading of reclaim_stat with lru_lock 



Rik van Riel pointed out reading reclaim_stat should be protected
lru_lock, otherwise vmscan might sweep 2x much pages.

This fault was introduced by

  commit 4f98a2fe
  Author: Rik van Riel <riel@redhat.com>
  Date:   Sat Oct 18 20:26:32 2008 -0700

    vmscan: split LRU lists into anon & file sets

Signed-off-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 15748048

mm/vmscan.c

+9 −11
Original line number Diff line number Diff line
@@ -1627,6 +1627,13 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc, 
		}

	}



	/*

	 * With swappiness at 100, anonymous and file have the same priority.

	 * This scanning priority is essentially the inverse of IO cost.

	 */

	anon_prio = sc->swappiness;

	file_prio = 200 - sc->swappiness;



	/*

	 * OK, so we have swap space and a fair amount of page cache

	 * pages.  We use the recently rotated / recently scanned
@@ -1638,27 +1645,17 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc, 
	 *

	 * anon in [0], file in [1]

	 */

	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {

	spin_lock_irq(&zone->lru_lock);

	if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {

		reclaim_stat->recent_scanned[0] /= 2;

		reclaim_stat->recent_rotated[0] /= 2;

		spin_unlock_irq(&zone->lru_lock);

	}



	if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {

		spin_lock_irq(&zone->lru_lock);

		reclaim_stat->recent_scanned[1] /= 2;

		reclaim_stat->recent_rotated[1] /= 2;

		spin_unlock_irq(&zone->lru_lock);

	}



	/*

	 * With swappiness at 100, anonymous and file have the same priority.

	 * This scanning priority is essentially the inverse of IO cost.

	 */

	anon_prio = sc->swappiness;

	file_prio = 200 - sc->swappiness;



	/*

	 * The amount of pressure on anon vs file pages is inversely

	 * proportional to the fraction of recently scanned pages on
@@ -1669,6 +1666,7 @@ static void get_scan_count(struct zone *zone, struct scan_control *sc, 


	fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);

	fp /= reclaim_stat->recent_rotated[1] + 1;

	spin_unlock_irq(&zone->lru_lock);



	fraction[0] = ap;

	fraction[1] = fp;