mm: memcontrol: give the kmem states more descriptive names

mm: memcontrol: give the kmem states more descriptive names

On any given memcg, the kmem accounting feature has three separate
states: not initialized, structures allocated, and actively accounting
slab memory.  These are represented through a combination of the
kmem_acct_activated and kmem_acct_active flags, which is confusing.

Convert to a kmem_state enum with the states NONE, ALLOCATED, and
ONLINE.  Then rename the functions to modify the state accordingly.
This follows the nomenclature of css object states more closely.

Signed-off-by: Johannes Weiner <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Cc: Tejun Heo <[email protected]>
Acked-by: Vladimir Davydov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>