[PATCH v2] vmscan: check all_unreclaimable in direct reclaim path

From: Minchan Kim
Date: Sun Sep 12 2010 - 12:32:14 EST

Adnrew, Please drop my old version and merge this verstion.
(old : vmscan-check-all_unreclaimable-in-direct-reclaim-path.patch)

* Changelog from v2
* remove inline - suggested by Andrew
* add function desription - suggeseted by Adnrew

== CUT HERE ==

Subject: [PATCH v2] vmscan: check all_unreclaimable in direct reclaim path

M. Vefa Bicakci reported 2.6.35 kernel hang up when hibernation on his
32bit 3GB mem machine. (https://bugzilla.kernel.org/show_bug.cgi?id=16771)
Also he was bisected first bad commit is below

commit bb21c7ce18eff8e6e7877ca1d06c6db719376e3c
Author: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Date: Fri Jun 4 14:15:05 2010 -0700

vmscan: fix do_try_to_free_pages() return value when priority==0 reclaim failure

At first impression, this seemed very strange because the above commit only
chenged function return value and hibernate_preallocate_memory() ignore
return value of shrink_all_memory(). But it's related.

Now, page allocation from hibernation code may enter infinite loop if
the system has highmem. The reasons are that vmscan don't care enough
OOM case when oom_killer_disabled.

The problem sequence is following as.

1. hibernation
2. oom_disable
3. alloc_pages
4. do_try_to_free_pages
if (scanning_global_lru(sc) && !all_unreclaimable)
return 1;

If kswapd is not freezed, it would set zone->all_unreclaimable to 1 and then
shrink_zones maybe return true(ie, all_unreclaimable is true).
so at last, alloc_pages could go to _nopage_. If it is, it should have no problem.

This patch adds all_unreclaimable check to protect in direct reclaim path, too.
It can care of hibernation OOM case and help bailout all_unreclaimable case slightly.

Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: M. Vefa Bicakci <bicave@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxx
Acked-by: Rafael J. Wysocki <rjw@xxxxxxx>
Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
---
mm/vmscan.c | 46 ++++++++++++++++++++++++++++++++++++++--------
1 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7870893..ecae0ef 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1877,12 +1877,11 @@ static void shrink_zone(int priority, struct zone *zone,
* If a zone is deemed to be full of pinned pages then just give it a light
* scan then give up on it.
*/
-static bool shrink_zones(int priority, struct zonelist *zonelist,
+static void shrink_zones(int priority, struct zonelist *zonelist,
struct scan_control *sc)
{
struct zoneref *z;
struct zone *zone;
- bool all_unreclaimable = true;

for_each_zone_zonelist_nodemask(zone, z, zonelist,
gfp_zone(sc->gfp_mask), sc->nodemask) {
@@ -1900,8 +1899,41 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
}

shrink_zone(priority, zone, sc);
- all_unreclaimable = false;
}
+}
+
+static bool zone_reclaimable(struct zone *zone)
+{
+ return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
+}
+
+/*
+ * As hibernation is going on, kswapd is freezed so that it can't mark
+ * the zone into all_unreclaimable. It can't handle OOM during hibernation.
+ * So let's check zone's unreclaimable in direct reclaim as well as kswapd.
+ */
+static bool all_unreclaimable(struct zonelist *zonelist,
+ struct scan_control *sc)
+{
+ struct zoneref *z;
+ struct zone *zone;
+ bool all_unreclaimable = true;
+
+ if (!scanning_global_lru(sc))
+ return false;
+
+ for_each_zone_zonelist_nodemask(zone, z, zonelist,
+ gfp_zone(sc->gfp_mask), sc->nodemask) {
+ if (!populated_zone(zone))
+ continue;
+ if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
+ continue;
+ if (zone_reclaimable(zone)) {
+ all_unreclaimable = false;
+ break;
+ }
+ }
+
return all_unreclaimable;
}

@@ -1925,7 +1957,6 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
struct scan_control *sc)
{
int priority;
- bool all_unreclaimable;
unsigned long total_scanned = 0;
struct reclaim_state *reclaim_state = current->reclaim_state;
struct zoneref *z;
@@ -1942,7 +1973,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
sc->nr_scanned = 0;
if (!priority)
disable_swap_token();
- all_unreclaimable = shrink_zones(priority, zonelist, sc);
+ shrink_zones(priority, zonelist, sc);
/*
* Don't shrink slabs when reclaiming memory from
* over limit cgroups
@@ -2004,7 +2035,7 @@ out:
return sc->nr_reclaimed;

/* top priority shrink_zones still had more to do? don't OOM, then */
- if (scanning_global_lru(sc) && !all_unreclaimable)
+ if (!all_unreclaimable(zonelist, sc))
return 1;

return 0;
@@ -2270,8 +2301,7 @@ loop_again:
total_scanned += sc.nr_scanned;
if (zone->all_unreclaimable)
continue;
- if (nr_slab == 0 &&
- zone->pages_scanned >= (zone_reclaimable_pages(zone) * 6))
+ if (nr_slab == 0 && !zone_reclaimable(zone))
zone->all_unreclaimable = 1;
/*
* If we've done a decent amount of scanning and
--
1.7.0.5


--
Kind regards,
Minchan Kim
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