mm: memcontrol: simplify the logic of objcg pinning memcg

The obj_cgroup_release() and memcg_reparent_objcgs() are serialized by the
css_set_lock.  We do not need to care about objcg->memcg being released in
the process of obj_cgroup_release().  So there is no need to pin memcg
before releasing objcg.  Remove those pinning logic to simplfy the code.

There are only two places that modifies the objcg->memcg.  One is the
initialization to objcg->memcg in the memcg_online_kmem(), another is
objcgs reparenting in the memcg_reparent_objcgs().  It is also impossible
for the two to run in parallel.  So xchg() is unnecessary and it is enough
to use WRITE_ONCE().

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Muchun Song <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Reviewed-by: Shakeel Butt <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Cc: Xiongchun Duan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions