From f91213cc1e44a0e5222f0b0bc61e6be6a252a154 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hugh@veritas.com>
Date: Sat, 3 Sep 2005 15:54:40 -0700
Subject: [PATCH] --- yaml --- r: 6854 b: refs/heads/master c:
 048c27fd72816b44e096997d1c6901c3abbfd45b h: refs/heads/master v: v3

---
 [refs]              |  2 +-
 trunk/mm/swapfile.c | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index 0901607bccd9..35898612b531 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 52b7efdbe5f5696fc80338560a3fc51e0b0a993c
+refs/heads/master: 048c27fd72816b44e096997d1c6901c3abbfd45b
diff --git a/trunk/mm/swapfile.c b/trunk/mm/swapfile.c
index fdee145afc6f..e675ae55f87d 100644
--- a/trunk/mm/swapfile.c
+++ b/trunk/mm/swapfile.c
@@ -56,8 +56,6 @@ static DECLARE_MUTEX(swapon_sem);
  */
 static DECLARE_RWSEM(swap_unplug_sem);
 
-#define SWAPFILE_CLUSTER 256
-
 void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
 {
 	swp_entry_t entry;
@@ -84,9 +82,13 @@ void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
 	up_read(&swap_unplug_sem);
 }
 
+#define SWAPFILE_CLUSTER	256
+#define LATENCY_LIMIT		256
+
 static inline unsigned long scan_swap_map(struct swap_info_struct *si)
 {
 	unsigned long offset, last_in_cluster;
+	int latency_ration = LATENCY_LIMIT;
 
 	/* 
 	 * We try to cluster swap pages by allocating them sequentially
@@ -117,6 +119,10 @@ static inline unsigned long scan_swap_map(struct swap_info_struct *si)
 				si->cluster_next = offset-SWAPFILE_CLUSTER-1;
 				goto cluster;
 			}
+			if (unlikely(--latency_ration < 0)) {
+				cond_resched();
+				latency_ration = LATENCY_LIMIT;
+			}
 		}
 		swap_device_lock(si);
 		goto lowest;
@@ -153,6 +159,10 @@ checks:	if (!(si->flags & SWP_WRITEOK))
 			swap_device_lock(si);
 			goto checks;
 		}
+		if (unlikely(--latency_ration < 0)) {
+			cond_resched();
+			latency_ration = LATENCY_LIMIT;
+		}
 	}
 	swap_device_lock(si);
 	goto lowest;