mm: compaction: do suspend compaction in workqueue

Move compact_nodes_suspend out of the direct early suspend workqueue
to avoid long delays in the suspend path on a heavily loaded system;
examples being heavily use of filesystem contending with the pages
that are trying to be compacted.

Signed-off-by: Yuan Jiangli <[email protected]>
Reviewed-on: http://gerrit.pcs.mot.com/535748
SLT-Approved: Slta Waiver <[email protected]>
Tested-by: Jira Key <[email protected]>
Reviewed-by: Christopher Fries <[email protected]>
Reviewed-by: Igor Kovalenko <[email protected]>
Reviewed-by: Klocwork kwcheck <[email protected]>
Submit-Approved: Jira Key <[email protected]>
Reviewed-by: Check Patch <[email protected]>

(cherry-pick from commit  6e202c2572708430f682987b2240eae50dadb1e3)

Change-Id: Ifcf8e0ff8f60d3c7f099d95653a43ba9651eeb28
Reviewed-on: http://gerrit.pcs.mot.com/540977
SLT-Approved: Slta Waiver <[email protected]>
Tested-by: Jira Key <[email protected]>
Reviewed-by: Yi-Wei Zhao <[email protected]>
Submit-Approved: Jira Key <[email protected]>

mm/compaction.c

@@ -1069,8 +1069,9 @@ unsigned long try_to_compact_pages(struct zonelist *zonelist,
 }
 
 #ifdef CONFIG_HAS_EARLYSUSPEND
+static struct work_struct compactnodes_w;
 static int compact_nodes(void);
-static void compact_nodes_suspend(struct early_suspend *s)
+static void compactnodes_work(struct work_struct *w)
 {
 	/* No point in being gun shy here since compact_zone()
 	 * will check suitability of compaction run per zone.
@@ -1080,6 +1081,13 @@ static void compact_nodes_suspend(struct early_suspend *s)
 	 * screen is off so there's no perceived user impact.
          */
 	compact_nodes();
+
+}
+
+
+static void compact_nodes_suspend(struct early_suspend *s)
+{
+	schedule_work(&compactnodes_w);
 }
 
 static struct early_suspend early_suspend_compaction_desc = {
@@ -1212,6 +1220,7 @@ void compaction_unregister_node(struct node *node)
 #ifdef CONFIG_HAS_EARLYSUSPEND
 static int  __init mem_compaction_init(void)
 {
+	INIT_WORK(&compactnodes_w, compactnodes_work);
 	register_early_suspend(&early_suspend_compaction_desc);
 	return 0;
 }