git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From fa1e512fac717f34e7c12d7a384c46e90a647392 Mon Sep 17 00:00:00 2001
   2 From: Yang Shi <yang.shi@linux.alibaba.com>
   3 Date: Fri, 2 Aug 2019 21:48:44 -0700
   4 Subject: mm: vmscan: check if mem cgroup is disabled or not before calling memcg slab shrinker
   5
   6 From: Yang Shi <yang.shi@linux.alibaba.com>
   7
   8 commit fa1e512fac717f34e7c12d7a384c46e90a647392 upstream.
   9
  10 Shakeel Butt reported premature oom on kernel with
  11 "cgroup_disable=memory" since mem_cgroup_is_root() returns false even
  12 though memcg is actually NULL.  The drop_caches is also broken.
  13
  14 It is because commit aeed1d325d42 ("mm/vmscan.c: generalize
  15 shrink_slab() calls in shrink_node()") removed the !memcg check before
  16 !mem_cgroup_is_root().  And, surprisingly root memcg is allocated even
  17 though memory cgroup is disabled by kernel boot parameter.
  18
  19 Add mem_cgroup_disabled() check to make reclaimer work as expected.
  20
  21 Link: http://lkml.kernel.org/r/1563385526-20805-1-git-send-email-yang.shi@linux.alibaba.com
  22 Fixes: aeed1d325d42 ("mm/vmscan.c: generalize shrink_slab() calls in shrink_node()")
  23 Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
  24 Reported-by: Shakeel Butt <shakeelb@google.com>
  25 Reviewed-by: Shakeel Butt <shakeelb@google.com>
  26 Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
  27 Acked-by: Michal Hocko <mhocko@suse.com>
  28 Cc: Jan Hadrava <had@kam.mff.cuni.cz>
  29 Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
  30 Cc: Johannes Weiner <hannes@cmpxchg.org>
  31 Cc: Roman Gushchin <guro@fb.com>
  32 Cc: Hugh Dickins <hughd@google.com>
  33 Cc: Qian Cai <cai@lca.pw>
  34 Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
  35 Cc: <stable@vger.kernel.org>    [4.19+]
  36 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  37 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  38 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  39
  40 ---
  41  mm/vmscan.c |    9 ++++++++-
  42  1 file changed, 8 insertions(+), 1 deletion(-)
  43
  44 --- a/mm/vmscan.c
  45 +++ b/mm/vmscan.c
  46 @@ -670,7 +670,14 @@ static unsigned long shrink_slab(gfp_t g
  47         unsigned long ret, freed = 0;
  48         struct shrinker *shrinker;
  49
  50 -       if (!mem_cgroup_is_root(memcg))
  51 +       /*
  52 +        * The root memcg might be allocated even though memcg is disabled
  53 +        * via "cgroup_disable=memory" boot parameter.  This could make
  54 +        * mem_cgroup_is_root() return false, then just run memcg slab
  55 +        * shrink, but skip global shrink.  This may result in premature
  56 +        * oom.
  57 +        */
  58 +       if (!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
  59                 return shrink_slab_memcg(gfp_mask, nid, memcg, priority);
  60
  61         if (!down_read_trylock(&shrinker_rwsem))