[Devel] [PATCH -RSS 1/1] Fix reclaim failure

[Balbir Singh]

This patch fixes the problem seen when a container goes over its limit, the
reclaim is unsuccessful and the application is terminated. The problem
is that all pages are by default added to the active list of the RSS
controller. When __isolate_lru_page() is called, it checks to see if
the list that the page is on (active or inactive) is the same as
what PageActive(page) returns. If this is not the case, the page is skipped.
In our case a page might not have the PG_active bit set and might be on
the active list of the container, thus we were ignoring those pages and
our reclaim fails, leading to the application being killed.

Signed-off-by: Balbir Singh <balbir at linux.vnet.ibm.com>
---

 mm/rss_container.c |   31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff -puN mm/rss_container.c~rss-fix-free-of-active-pages mm/rss_container.c
--- linux-2.6.22-rc2-mm1/mm/rss_container.c~rss-fix-free-of-active-pages	2007-06-04 19:48:56.000000000 +0530
+++ linux-2.6.22-rc2-mm1-balbir/mm/rss_container.c	2007-06-04 19:50:18.000000000 +0530
@@ -205,18 +205,37 @@ void container_rss_move_lists(struct pag
 }
 
 static unsigned long isolate_container_pages(unsigned long nr_to_scan,
-		struct list_head *src, struct list_head *dst,
-		unsigned long *scanned, struct zone *zone, int mode)
+		struct rss_container *rss, struct list_head *dst,
+		unsigned long *scanned, struct zone *zone, int mode,
+		int active)
 {
 	unsigned long nr_taken = 0;
 	struct page *page;
 	struct page_container *pc;
 	unsigned long scan;
 	LIST_HEAD(pc_list);
+	struct list_head *src;
+
+ 	src = active ? &rss->active_list : &rss->inactive_list;
 
 	for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
 		pc = list_entry(src->prev, struct page_container, list);
 		page = pc->page;
+
+		/*
+		 * We might have got our active, inactive lists
+		 * incorrect, fix it here
+		 */
+		if (active && !PageActive(page)) {
+			list_move(&pc->list, &rss->inactive_list);
+			scan--;
+			continue;
+		} else if (!active && PageActive(page)) {
+			list_move(&pc->list, &rss->active_list);
+			scan--;
+			continue;
+		}
+
 		/*
 		 * TODO: now we hold all the pages in one... ok, two lists
 		 * and skip the pages from another zones with the check
@@ -249,12 +268,8 @@ unsigned long isolate_pages_in_container
 
 	/* we are called with zone->lru_lock held with irqs disabled */
 	spin_lock(&rss->res.lock);
-	if (active)
-		ret = isolate_container_pages(nr_to_scan, &rss->active_list,
-				dst, scanned, zone, mode);
-	else
-		ret = isolate_container_pages(nr_to_scan, &rss->inactive_list,
-				dst, scanned, zone, mode);
+	ret = isolate_container_pages(nr_to_scan, rss, dst, scanned, zone,
+					mode, active);
 	spin_unlock(&rss->res.lock);
 	return ret;
 }
_

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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