ANDROID: implement wrapper for reverse migration

Reverse migration is used to do the balancing the occupancy of memory
zones in a node in the system whose imabalance may be caused by
migration of pages to other zones by an operation, eg: hotremove and
then hotadding the same memory. In this case there is a lot of free
memory in newly hotadd memory which can be filled up by the previous
migrated pages(as part of offline/hotremove) thus may free up some
pressure in other zones of the node.

Upstream discussion: https://lore.kernel.org/patchwork/cover/1382106/

Change-Id: Ib3137dab0db66ecf6858c4077dcadb9dfd0c6b1c
Bug: 175403896
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>

include/linux/compaction.h

@@ -182,6 +182,8 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 extern int kcompactd_run(int nid);
 extern void kcompactd_stop(int nid);
 extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx);
+extern unsigned long isolate_and_split_free_page(struct page *page,
+				struct list_head *list);
 
 #else
 static inline void reset_isolation_suitable(pg_data_t *pgdat)
@@ -236,6 +238,12 @@ static inline void wakeup_kcompactd(pg_data_t *pgdat,
 {
 }
 
+static unsigned long isolate_and_split_free_page(struct page *page,
+				struct list_head *list)
+{
+	return 0;
+}
+
 #endif /* CONFIG_COMPACTION */
 
 struct node;

include/linux/mmzone.h

@@ -1014,6 +1014,7 @@ extern struct pglist_data contig_page_data;
 extern struct pglist_data *first_online_pgdat(void);
 extern struct pglist_data *next_online_pgdat(struct pglist_data *pgdat);
 extern struct zone *next_zone(struct zone *zone);
+extern int isolate_anon_lru_page(struct page *page);
 
 /**
  * for_each_online_pgdat - helper macro to iterate over all online nodes

mm/compaction.c

@@ -763,6 +763,29 @@ isolate_freepages_range(struct compact_control *cc,
 	return pfn;
 }
 
+unsigned long isolate_and_split_free_page(struct page *page,
+						struct list_head *list)
+{
+	unsigned long isolated;
+	unsigned int order;
+
+	if (!PageBuddy(page))
+		return 0;
+
+	order = buddy_order(page);
+	isolated = __isolate_free_page(page, order);
+	if (!isolated)
+		return 0;
+
+	set_page_private(page, order);
+	list_add(&page->lru, list);
+
+	split_map_pages(list);
+
+	return isolated;
+}
+EXPORT_SYMBOL_GPL(isolate_and_split_free_page);
+
 /* Similar to reclaim, but different enough that they don't share logic */
 static bool too_many_isolated(pg_data_t *pgdat)
 {

mm/migrate.c

@@ -172,6 +172,7 @@ void putback_movable_pages(struct list_head *l)
 		}
 	}
 }
+EXPORT_SYMBOL_GPL(putback_movable_pages);
 
 /*
  * Restore a potential migration pte to a working pte entry
@@ -1509,6 +1510,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
 
 	return rc;
 }
+EXPORT_SYMBOL_GPL(migrate_pages);
 
 struct page *alloc_migration_target(struct page *page, unsigned long private)
 {

mm/page_alloc.c

@@ -537,6 +537,24 @@ unsigned long get_pfnblock_flags_mask(struct page *page, unsigned long pfn,
 {
 	return __get_pfnblock_flags_mask(page, pfn, mask);
 }
+EXPORT_SYMBOL_GPL(get_pfnblock_flags_mask);
+
+int isolate_anon_lru_page(struct page *page)
+{
+	int ret;
+
+	if (!PageLRU(page) || !PageAnon(page))
+		return -EINVAL;
+
+	if (!get_page_unless_zero(page))
+		return -EINVAL;
+
+	ret = isolate_lru_page(page);
+	put_page(page);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(isolate_anon_lru_page);
 
 static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned long pfn)
 {