mm: oom_kill: clean up victim marking and exiting interfaces

Rename unmark_oom_victim() to exit_oom_victim().  Marking and unmarking
are related in functionality, but the interface is not symmetrical at
all: one is an internal OOM killer function used during the killing, the
other is for an OOM victim to signal its own death on exit later on.
This has locking implications, see follow-up changes.

While at it, rename mark_tsk_oom_victim() to mark_oom_victim(), which
is easier on the eye.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/oom.h b/include/linux/oom.h
index 44b2f6f..a8e6a49 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -47,9 +47,7 @@
 	return !!(p->signal->oom_flags & OOM_FLAG_ORIGIN);
 }
 
-extern void mark_tsk_oom_victim(struct task_struct *tsk);
-
-extern void unmark_oom_victim(void);
+extern void mark_oom_victim(struct task_struct *tsk);
 
 extern unsigned long oom_badness(struct task_struct *p,
 		struct mem_cgroup *memcg, const nodemask_t *nodemask,
@@ -75,6 +73,9 @@
 
 extern bool out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
 		int order, nodemask_t *mask, bool force_kill);
+
+extern void exit_oom_victim(void);
+
 extern int register_oom_notifier(struct notifier_block *nb);
 extern int unregister_oom_notifier(struct notifier_block *nb);