mm, oom: pass an oom order of -1 when triggered by sysrq

The force_kill member of struct oom_control isn't needed if an order of -1
is used instead.  This is the same as order == -1 in struct
compact_control which requires full memory compaction.

This patch introduces no functional change.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/tty/sysrq.c

@@ -358,8 +358,7 @@ static void moom_callback(struct work_struct *ignored)
 		.zonelist = node_zonelist(first_memory_node, gfp_mask),
 		.nodemask = NULL,
 		.gfp_mask = gfp_mask,
-		.order = 0,
-		.force_kill = true,
+		.order = -1,
 	};
 
 	mutex_lock(&oom_lock);

include/linux/oom.h

@@ -17,7 +17,6 @@ struct oom_control {
 	nodemask_t	*nodemask;
 	gfp_t		gfp_mask;
 	int		order;
-	bool		force_kill;
 };
 
 /*

mm/memcontrol.c

@@ -1550,7 +1550,6 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
 		.nodemask = NULL,
 		.gfp_mask = gfp_mask,
 		.order = order,
-		.force_kill = false,
 	};
 	struct mem_cgroup *iter;
 	unsigned long chosen_points = 0;

mm/oom_kill.c

@@ -265,7 +265,7 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
 	 * Don't allow any other task to have access to the reserves.
 	 */
 	if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
-		if (!oc->force_kill)
+		if (oc->order != -1)
 			return OOM_SCAN_ABORT;
 	}
 	if (!task->mm)
@@ -278,7 +278,7 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
 	if (oom_task_origin(task))
 		return OOM_SCAN_SELECT;
 
-	if (task_will_free_mem(task) && !oc->force_kill)
+	if (task_will_free_mem(task) && oc->order != -1)
 		return OOM_SCAN_ABORT;
 
 	return OOM_SCAN_OK;
@@ -718,7 +718,6 @@ void pagefault_out_of_memory(void)
 		.nodemask = NULL,
 		.gfp_mask = 0,
 		.order = 0,
-		.force_kill = false,
 	};
 
 	if (mem_cgroup_oom_synchronize(true))

mm/page_alloc.c

@@ -2698,7 +2698,6 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
 		.nodemask = ac->nodemask,
 		.gfp_mask = gfp_mask,
 		.order = order,
-		.force_kill = false,
 	};
 	struct page *page;