memcg: make oom less frequently

memcg: make oom less frequently

In previous implementation, mem_cgroup_try_charge checked the return
value of mem_cgroup_try_to_free_pages, and just retried if some pages
had been reclaimed.
But now, try_charge(and mem_cgroup_hierarchical_reclaim called from it)
only checks whether the usage is less than the limit.

This patch tries to change the behavior as before to cause oom less
frequently.

Signed-off-by: Daisuke Nishimura <[email protected]>
Acked-by: Balbir Singh <[email protected]>
Acked-by: KAMEZAWA Hiroyuki <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Li Zefan <[email protected]>
Cc: Paul Menage <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>