+ mm-memcontrol-fix-get_active_memcg-return-value.patch added to -mm tree

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The patch titled
     Subject: mm: memcontrol: fix get_active_memcg return value
has been added to the -mm tree.  Its filename is
     mm-memcontrol-fix-get_active_memcg-return-value.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-fix-get_active_memcg-return-value.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-fix-get_active_memcg-return-value.patch

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------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm: memcontrol: fix get_active_memcg return value

We use a global percpu int_active_memcg variable to store the remote memcg
when we are in the interrupt context.  But get_active_memcg always return
the current->active_memcg or root_mem_cgroup.  The remote memcg (set in
the interrupt context) is ignored.  This is not what we want.  So fix it.

Link: https://lkml.kernel.org/r/20210223091101.42150-1-songmuchun@xxxxxxxxxxxxx
Fixes: 37d5985c003d ("mm: kmem: prepare remote memcg charging infra for interrupt contexts")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
Reviewed-by: Roman Gushchin <guro@xxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/memcontrol.c |   10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

--- a/mm/memcontrol.c~mm-memcontrol-fix-get_active_memcg-return-value
+++ a/mm/memcontrol.c
@@ -1061,13 +1061,9 @@ static __always_inline struct mem_cgroup
 
 	rcu_read_lock();
 	memcg = active_memcg();
-	if (memcg) {
-		/* current->active_memcg must hold a ref. */
-		if (WARN_ON_ONCE(!css_tryget(&memcg->css)))
-			memcg = root_mem_cgroup;
-		else
-			memcg = current->active_memcg;
-	}
+	/* remote memcg must hold a ref. */
+	if (memcg && WARN_ON_ONCE(!css_tryget(&memcg->css)))
+		memcg = root_mem_cgroup;
 	rcu_read_unlock();
 
 	return memcg;
_

Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are

mm-memcontrol-optimize-per-lruvec-stats-counter-memory-usage.patch
mm-memcontrol-fix-nr_anon_thps-accounting-in-charge-moving.patch
mm-memcontrol-convert-nr_anon_thps-account-to-pages.patch
mm-memcontrol-convert-nr_file_thps-account-to-pages.patch
mm-memcontrol-convert-nr_shmem_thps-account-to-pages.patch
mm-memcontrol-convert-nr_shmem_pmdmapped-account-to-pages.patch
mm-memcontrol-convert-nr_file_pmdmapped-account-to-pages.patch
mm-memcontrol-make-the-slab-calculation-consistent.patch
mm-memcontrol-replace-the-loop-with-a-list_for_each_entry.patch
mm-memcontrol-fix-swap-undercounting-in-cgroup2.patch
mm-memcontrol-fix-get_active_memcg-return-value.patch
hugetlb-convert-page_huge_active-hpagemigratable-flag-fix.patch




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