memcg, kmem: further deprecate kmem.limit_in_bytes

memcg, kmem: further deprecate kmem.limit_in_bytes

The deprecation process of kmem.limit_in_bytes started with the commit
0158115f702 ("memcg, kmem: deprecate kmem.limit_in_bytes") which also
explains in detail the motivation behind the deprecation.  To summarize,
it is the unexpected behavior on hitting the kmem limit.  This patch
moves the deprecation process to the next stage by disallowing to set
the kmem limit.  In future we might just remove the kmem.limit_in_bytes
file completely.

[[email protected]: s/ENOTSUPP/EOPNOTSUPP/]
[[email protected]: mark cancel_charge() inline]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Shakeel Butt <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Cc: Vasily Averin <[email protected]>
Cc: Johannes Weiner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>