mm: memcg: shorten preempt-disabled section around event checks

mm: memcg: shorten preempt-disabled section around event checks

Only the ratelimit checks themselves have to run with preemption
disabled, the resulting actions - checking for usage thresholds,
updating the soft limit tree - can and should run with preemption
enabled.

Signed-off-by: Johannes Weiner <[email protected]>
Reported-by: Yong Zhang <[email protected]>
Tested-by: Yong Zhang <[email protected]>
Reported-by: Luis Henriques <[email protected]>
Tested-by: Luis Henriques <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Acked-by: KAMEZAWA Hiroyuki <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>