Zone reclaim V4 [1/3]: resurrect may_swap

[Christoph Lameter <clameter@sgi.com>]

Resurrect may_swap in struct scan_control

Patch against 2.6.15-rc5-mm3 to undo the patch to remove may_writepage.

Not needed for 2.6.14 / 2.6.15-rc6.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.15-rc5-mm3/mm/vmscan.c
===================================================================
--- linux-2.6.15-rc5-mm3.orig/mm/vmscan.c	2005-12-20 15:46:51.000000000 -0800
+++ linux-2.6.15-rc5-mm3/mm/vmscan.c	2005-12-21 12:32:43.000000000 -0800
@@ -71,6 +71,9 @@ struct scan_control {
 
 	int may_writepage;
 
+	/* Can pages be swapped as part of reclaim? */
+	int may_swap;
+
 	/* This context's SWAP_CLUSTER_MAX. If freeing memory for
 	 * suspend, we effectively ignore SWAP_CLUSTER_MAX.
 	 * In this context, it doesn't matter that we scan the
@@ -457,6 +460,8 @@ static int shrink_list(struct list_head 
 		 * Try to allocate it some swap space here.
 		 */
 		if (PageAnon(page) && !PageSwapCache(page)) {
+			if (!sc->may_swap)
+				goto keep_locked;
 			if (!add_to_swap(page, GFP_ATOMIC))
 				goto activate_locked;
 		}
@@ -1180,6 +1185,7 @@ int try_to_free_pages(struct zone **zone
 
 	sc.gfp_mask = gfp_mask;
 	sc.may_writepage = 0;
+	sc.may_swap = 1;
 
 	count_event(ALLOCSTALL);
 
@@ -1282,6 +1288,7 @@ loop_again:
 	total_reclaimed = 0;
 	sc.gfp_mask = GFP_KERNEL;
 	sc.may_writepage = 0;
+	sc.may_swap = 1;
 	sc.nr_mapped = global_page_state(NR_MAPPED);
 
 	count_event(PAGEOUTRUN);