Re: cgroup oom regression introduced by 6a5ce1b94e1e5979f8db579f77d6e08a5f44c13b

[Minchan Kim <minchan.kim@gmail.com>]

On Sat, Sep 18, 2010 at 08:52:34AM -0400, caiqian@redhat.com wrote:
> This test hung the kernel without triggering oom.
> # mount -t cgroup -o memory none /cgroup/memory/
> # mkdir /cgroup/memory/A
> # echo $$ >/cgroup/memory/A/tasks
> # echo 4096M >/cgroup/memory/A/memory.limit_in_bytes
> # echo 4096M >/cgroup/memory/A/memory.memsw.limit_in_bytes
> # use malloc to allocate more than 4G memory.
> 
> Sometimes, this had been thrown out of console,
> localhost.localdomain login: INFO: task sm1:5065 blocked for more than 120 seconds.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> sm1           D 00000000fffca130     0  5065   5051 0x00000080
>  ffff880c5f419c38 0000000000000086 ffff880c5f419bc8 ffffffff81034ca8
>  ffff880100000000 0000000000015440 ffff880c608ab4e0 0000000000015440
>  ffff880c608aba40 ffff880c5f419fd8 ffff880c608aba48 ffff880c5f419fd8
> Call Trace:
>  [<ffffffff81034ca8>] ? pvclock_clocksource_read+0x58/0xd0
>  [<ffffffff810f2c60>] ? sync_page+0x0/0x50
>  [<ffffffff81492553>] io_schedule+0x73/0xc0
>  [<ffffffff810f2c9d>] sync_page+0x3d/0x50
>  [<ffffffff81492cba>] __wait_on_bit_lock+0x5a/0xc0
>  [<ffffffff810f2c37>] __lock_page+0x67/0x70
>  [<ffffffff8107cf90>] ? wake_bit_function+0x0/0x50
>  [<ffffffff810f2a6e>] ? find_get_page+0x1e/0xa0
>  [<ffffffff810f4a5c>] filemap_fault+0x33c/0x450
>  [<ffffffff81110524>] __do_fault+0x54/0x550
>  [<ffffffff8113f30a>] ? __mem_cgroup_commit_charge+0x5a/0xa0
>  [<ffffffff811132a2>] handle_mm_fault+0x1c2/0xc70
>  [<ffffffff8149809c>] do_page_fault+0x11c/0x320
>  [<ffffffff81494cd5>] page_fault+0x25/0x30
> 
> Reverted the following commit from mmotm tree made the problem go away.
> commit 6a5ce1b94e1e5979f8db579f77d6e08a5f44c13b
> Author: Minchan Kim <minchan.kim@gmail.com>
> Date:   Thu Sep 16 01:17:26 2010 +0200
> 
>     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 bisected
>     the regression to
>     
>       commit bb21c7ce18eff8e6e7877ca1d06c6db719376e3c
>       Author: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>       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 freozen, 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.
>     
>     Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>     Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
>     Reported-by: M. Vefa Bicakci <bicave@superonline.com>
>     Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
>     Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
>     Cc: Rik van Riel <riel@redhat.com>
>     Cc: <stable@kernel.org>
>     Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 225a759..f56a8c3 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1804,12 +1804,11 @@ 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) {
> @@ -1827,8 +1826,36 @@ static bool shrink_zones(int priority, struct zonelist *zonelist,
>  		}
>  
>  		shrink_zone(priority, zone, sc);
> -		all_unreclaimable = false;
>  	}
> +}
> +
> +static inline bool zone_reclaimable(struct zone *zone)
> +{
> +	return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
> +}
> +
> +static inline 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;
>  }
>  
> @@ -1852,7 +1879,6 @@ 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;
> @@ -1869,7 +1895,7 @@ 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
> @@ -1931,7 +1957,7 @@ 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;
> @@ -2197,8 +2223,7 @@ 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

Thanks for the reporting. 
Could you test below patch?