tree 834ae6fb4e367dfccb8394c9baf84a94e262ae72
parent a6c135bb1a59b5d67c8c45b214d3427d65dd7c00
author Michal Hocko <mhocko@suse.com> 1567206290 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1567213250 -0700

mm, memcg: do not set reclaim_state on soft limit reclaim

Adric Blake has noticed[1] the following warning:

  WARNING: CPU: 7 PID: 175 at mm/vmscan.c:245 set_task_reclaim_state+0x1e/0x40
  [...]
  Call Trace:
   mem_cgroup_shrink_node+0x9b/0x1d0
   mem_cgroup_soft_limit_reclaim+0x10c/0x3a0
   balance_pgdat+0x276/0x540
   kswapd+0x200/0x3f0
   ? wait_woken+0x80/0x80
   kthread+0xfd/0x130
   ? balance_pgdat+0x540/0x540
   ? kthread_park+0x80/0x80
   ret_from_fork+0x35/0x40
  ---[ end trace 727343df67b2398a ]---

which tells us that soft limit reclaim is about to overwrite the
reclaim_state configured up in the call chain (kswapd in this case but
the direct reclaim is equally possible).  This means that reclaim stats
would get misleading once the soft reclaim returns and another reclaim
is done.

Fix the warning by dropping set_task_reclaim_state from the soft reclaim
which is always called with reclaim_state set up.

[1] http://lkml.kernel.org/r/CAE1jjeePxYPvw1mw2B3v803xHVR_BNnz0hQUY_JDMN8ny29M6w@mail.gmail.com

Link: http://lkml.kernel.org/r/20190828071808.20410-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Adric Blake <promarbler14@gmail.com>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hillf Danton <hdanton@sina.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>