The patch titled
Subject: mm,vmscan: don't pretend forward progress upon shrinker_rwsem contention
has been added to the -mm tree. Its filename is
mmvmscan-dont-pretend-forward-progress-upon-shrinker_rwsem-contention.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mmvmscan-dont-pretend-forward-progress-upon-shrinker_rwsem-contention.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mmvmscan-dont-pretend-forward-progress-upon-shrinker_rwsem-contention.patch
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------------------------------------------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Subject: mm,vmscan: don't pretend forward progress upon shrinker_rwsem contention
Since we no longer use return value of shrink_slab() for normal reclaim,
the comment is no longer true. If some do_shrink_slab() call takes
unexpectedly long (root cause of stall is currently unknown) when
register_shrinker()/unregister_shrinker() is pending, trying to drop
caches via /proc/sys/vm/drop_caches could become infinite cond_resched()
loop if many mem_cgroup are defined. For safety, let's not pretend
forward progress.
Link: http://lkml.kernel.org/r/201802202229.GGF26507.LVFtMSOOHFJOQF@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Cc: Glauber Costa <glommer@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff -puN mm/vmscan.c~mmvmscan-dont-pretend-forward-progress-upon-shrinker_rwsem-contention mm/vmscan.c
--- a/mm/vmscan.c~mmvmscan-dont-pretend-forward-progress-upon-shrinker_rwsem-contention
+++ a/mm/vmscan.c
@@ -442,16 +442,8 @@ static unsigned long shrink_slab(gfp_t g
if (memcg && (!memcg_kmem_enabled() || !mem_cgroup_online(memcg)))
return 0;
- if (!down_read_trylock(&shrinker_rwsem)) {
- /*
- * If we would return 0, our callers would understand that we
- * have nothing else to shrink and give up trying. By returning
- * 1 we keep it going and assume we'll be able to shrink next
- * time.
- */
- freed = 1;
+ if (!down_read_trylock(&shrinker_rwsem))
goto out;
- }
list_for_each_entry(shrinker, &shrinker_list, list) {
struct shrink_control sc = {
_
Patches currently in -mm which might be from penguin-kernel@xxxxxxxxxxxxxxxxxxx are
dentry-fix-kmemcheck-splat-at-take_dentry_name_snapshot.patch
mmvmscan-dont-pretend-forward-progress-upon-shrinker_rwsem-contention.patch
mmvmscan-mark-register_shrinker-as-__must_check.patch
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