The patch titled
vmscan: all_unreclaimable() use zone->all_unreclaimable as a name
has been removed from the -mm tree. Its filename was
vmscan-all_unreclaimable-use-zone-all_unreclaimable-as-a-name.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: vmscan: all_unreclaimable() use zone->all_unreclaimable as a name
From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
all_unreclaimable check in direct reclaim has been introduced at 2.6.19
by following commit.
2006 Sep 25; commit 408d8544; oom: use unreclaimable info
And it went through strange history. firstly, following commit broke
the logic unintentionally.
2008 Apr 29; commit a41f24ea; page allocator: smarter retry of
costly-order allocations
Two years later, I've found obvious meaningless code fragment and
restored original intention by following commit.
2010 Jun 04; commit bb21c7ce; vmscan: fix do_try_to_free_pages()
return value when priority==0
But, the logic didn't works when 32bit highmem system goes hibernation
and Minchan slightly changed the algorithm and fixed it .
2010 Sep 22: commit d1908362: vmscan: check all_unreclaimable
in direct reclaim path
But, recently, Andrey Vagin found the new corner case. Look,
struct zone {
..
int all_unreclaimable;
..
unsigned long pages_scanned;
..
}
zone->all_unreclaimable and zone->pages_scanned are neigher atomic
variables nor protected by lock. Therefore zones can become a state of
zone->page_scanned=0 and zone->all_unreclaimable=1. In this case, current
all_unreclaimable() return false even though zone->all_unreclaimabe=1.
This resulted in the kernel hanging up when executing a loop of the form
1. fork
2. mmap
3. touch memory
4. read memory
5. munmmap
as described in
http://www.gossamer-threads.com/lists/linux/kernel/1348725#1348725
Is this ignorable minor issue? No. Unfortunately, x86 has very small dma
zone and it become zone->all_unreclamble=1 easily. and if it become
all_unreclaimable=1, it never restore all_unreclaimable=0. Why? if
all_unreclaimable=1, vmscan only try DEF_PRIORITY reclaim and
a-few-lru-pages>>DEF_PRIORITY always makes 0. that mean no page scan at
all!
Eventually, oom-killer never works on such systems. That said, we can't
use zone->pages_scanned for this purpose. This patch restore
all_unreclaimable() use zone->all_unreclaimable as old. and in addition,
to add oom_killer_disabled check to avoid reintroduce the issue of commit
d1908362 ("vmscan: check all_unreclaimable in direct reclaim path").
Reported-by: Andrey Vagin <avagin@xxxxxxxxxx>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)
diff -puN mm/vmscan.c~vmscan-all_unreclaimable-use-zone-all_unreclaimable-as-a-name mm/vmscan.c
--- a/mm/vmscan.c~vmscan-all_unreclaimable-use-zone-all_unreclaimable-as-a-name
+++ a/mm/vmscan.c
@@ -41,6 +41,7 @@
#include <linux/memcontrol.h>
#include <linux/delayacct.h>
#include <linux/sysctl.h>
+#include <linux/oom.h>
#include <asm/tlbflush.h>
#include <asm/div64.h>
@@ -1988,17 +1989,12 @@ static bool zone_reclaimable(struct 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.
- */
+/* All zones in zonelist are unreclaimable? */
static bool all_unreclaimable(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) {
@@ -2006,13 +2002,11 @@ static bool all_unreclaimable(struct zon
continue;
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;
- if (zone_reclaimable(zone)) {
- all_unreclaimable = false;
- break;
- }
+ if (!zone->all_unreclaimable)
+ return false;
}
- return all_unreclaimable;
+ return true;
}
/*
@@ -2108,6 +2102,14 @@ out:
if (sc->nr_reclaimed)
return sc->nr_reclaimed;
+ /*
+ * As hibernation is going on, kswapd is freezed so that it can't mark
+ * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
+ * check.
+ */
+ if (oom_killer_disabled)
+ return 0;
+
/* top priority shrink_zones still had more to do? don't OOM, then */
if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc))
return 1;
_
Patches currently in -mm which might be from kosaki.motohiro@xxxxxxxxxxxxxx are
origin.patch
mm-per-node-vmstat-show-proper-vmstats.patch
mm-per-node-vmstat-show-proper-vmstats-fix.patch
mm-increase-reclaim_distance-to-30.patch
mm-introduce-wait_on_page_locked_killable.patch
x86mm-make-pagefault-killable.patch
mm-mem-hotplug-fix-section-mismatch-setup_per_zone_inactive_ratio-should-be-__meminit.patch
mm-mem-hotplug-recalculate-lowmem_reserve-when-memory-hotplug-occur.patch
mm-mem-hotplug-update-pcp-stat_threshold-when-memory-hotplug-occur.patch
mm-mem-hotplug-update-pcp-stat_threshold-when-memory-hotplug-occur-fix.patch
mm-convert-vma-vm_flags-to-64-bit.patch
mm-add-__nocast-attribute-to-vm_flags.patch
fremap-convert-vm_flags-to-unsigned-long-long.patch
procfs-convert-vm_flags-to-unsigned-long-long.patch
oom-replace-pf_oom_origin-with-toggling-oom_score_adj.patch
oom-replace-pf_oom_origin-with-toggling-oom_score_adj-update.patch
mm-batch-activate_page-to-reduce-lock-contention.patch
mm-move-enum-vm_event_item-into-a-standalone-header-file.patch
memcg-count-the-soft_limit-reclaim-in-global-background-reclaim.patch
memcg-add-stats-to-monitor-soft_limit-reclaim.patch
add-the-pagefault-count-into-memcg-stats.patch
add-the-pagefault-count-into-memcg-stats-fix.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch
kexec-remove-kmsg_dump_kexec.patch
kexec-remove-kmsg_dump_kexec-fix.patch
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