queue-4.4/memcg-make-it-work-on-sparse-non-0-node-systems.patch

   1 From 3e8589963773a5c23e2f1fe4bcad0e9a90b7f471 Mon Sep 17 00:00:00 2001
   2 From: Jiri Slaby <jslaby@suse.cz>
   3 Date: Fri, 31 May 2019 22:30:26 -0700
   4 Subject: memcg: make it work on sparse non-0-node systems
   5
   6 From: Jiri Slaby <jslaby@suse.cz>
   7
   8 commit 3e8589963773a5c23e2f1fe4bcad0e9a90b7f471 upstream.
   9
  10 We have a single node system with node 0 disabled:
  11   Scanning NUMA topology in Northbridge 24
  12   Number of physical nodes 2
  13   Skipping disabled node 0
  14   Node 1 MemBase 0000000000000000 Limit 00000000fbff0000
  15   NODE_DATA(1) allocated [mem 0xfbfda000-0xfbfeffff]
  16
  17 This causes crashes in memcg when system boots:
  18   BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  19   #PF error: [normal kernel read fault]
  20 ...
  21   RIP: 0010:list_lru_add+0x94/0x170
  22 ...
  23   Call Trace:
  24    d_lru_add+0x44/0x50
  25    dput.part.34+0xfc/0x110
  26    __fput+0x108/0x230
  27    task_work_run+0x9f/0xc0
  28    exit_to_usermode_loop+0xf5/0x100
  29
  30 It is reproducible as far as 4.12.  I did not try older kernels.  You have
  31 to have a new enough systemd, e.g.  241 (the reason is unknown -- was not
  32 investigated).  Cannot be reproduced with systemd 234.
  33
  34 The system crashes because the size of lru array is never updated in
  35 memcg_update_all_list_lrus and the reads are past the zero-sized array,
  36 causing dereferences of random memory.
  37
  38 The root cause are list_lru_memcg_aware checks in the list_lru code.  The
  39 test in list_lru_memcg_aware is broken: it assumes node 0 is always
  40 present, but it is not true on some systems as can be seen above.
  41
  42 So fix this by avoiding checks on node 0.  Remember the memcg-awareness by
  43 a bool flag in struct list_lru.
  44
  45 Link: http://lkml.kernel.org/r/20190522091940.3615-1-jslaby@suse.cz
  46 Fixes: 60d3fd32a7a9 ("list_lru: introduce per-memcg lists")
  47 Signed-off-by: Jiri Slaby <jslaby@suse.cz>
  48 Acked-by: Michal Hocko <mhocko@suse.com>
  49 Suggested-by: Vladimir Davydov <vdavydov.dev@gmail.com>
  50 Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>
  51 Reviewed-by: Shakeel Butt <shakeelb@google.com>
  52 Cc: Johannes Weiner <hannes@cmpxchg.org>
  53 Cc: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
  54 Cc: <stable@vger.kernel.org>
  55 Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
  56 Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  57 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  58
  59 ---
  60  include/linux/list_lru.h |    1 +
  61  mm/list_lru.c            |    8 +++-----
  62  2 files changed, 4 insertions(+), 5 deletions(-)
  63
  64 --- a/include/linux/list_lru.h
  65 +++ b/include/linux/list_lru.h
  66 @@ -51,6 +51,7 @@ struct list_lru {
  67         struct list_lru_node    *node;
  68  #ifdef CONFIG_MEMCG_KMEM
  69         struct list_head        list;
  70 +       bool                    memcg_aware;
  71  #endif
  72  };
  73
  74 --- a/mm/list_lru.c
  75 +++ b/mm/list_lru.c
  76 @@ -42,11 +42,7 @@ static void list_lru_unregister(struct l
  77  #ifdef CONFIG_MEMCG_KMEM
  78  static inline bool list_lru_memcg_aware(struct list_lru *lru)
  79  {
  80 -       /*
  81 -        * This needs node 0 to be always present, even
  82 -        * in the systems supporting sparse numa ids.
  83 -        */
  84 -       return !!lru->node[0].memcg_lrus;
  85 +       return lru->memcg_aware;
  86  }
  87
  88  static inline struct list_lru_one *
  89 @@ -389,6 +385,8 @@ static int memcg_init_list_lru(struct li
  90  {
  91         int i;
  92
  93 +       lru->memcg_aware = memcg_aware;
  94 +
  95         if (!memcg_aware)
  96                 return 0;
  97