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/all/[email protected]/

Port to ACK6.6: Fold in following simple fixes from ACK6.1:

commit d0652b3 ("ANDROID: inline isolate_and_split_free_page")
commit 8a98feb ("ANDROID: mm: compaction: fix isolate_and_split_free_page() redefinition")

Bug: 201263307
Signed-off-by: Charan Teja Reddy <[email protected]>
Signed-off-by: Sukadev Bhattiprolu <[email protected]>
Change-Id: Ib3137dab0db66ecf6858c4077dcadb9dfd0c6b1c

Author: Charan Teja Reddy

include/linux/compaction.h

@@ -101,6 +101,8 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 extern void __meminit kcompactd_run(int nid);
 extern void __meminit 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)
@@ -125,6 +127,12 @@ static inline void wakeup_kcompactd(pg_data_t *pgdat,
 {
 }
 
+static inline 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

@@ -1569,6 +1569,7 @@ static inline struct pglist_data *NODE_DATA(int nid)
 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

@@ -784,6 +784,31 @@ isolate_freepages_range(struct compact_control *cc,
 	return pfn;
 }
 
+#ifdef CONFIG_COMPACTION
+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);
+#endif
+
 /* Similar to reclaim, but different enough that they don't share logic */
 static bool too_many_isolated(struct compact_control *cc)
 {

mm/migrate.c

@@ -176,6 +176,7 @@ void putback_movable_pages(struct list_head *l)
 		}
 	}
 }
+EXPORT_SYMBOL_GPL(putback_movable_pages);
 
 /*
  * Restore a potential migration pte to a working pte entry
@@ -1987,6 +1988,7 @@ int migrate_pages(struct list_head *from, new_folio_t get_new_folio,
 
 	return rc_gather;
 }
+EXPORT_SYMBOL_GPL(migrate_pages);
 
 struct folio *alloc_migration_target(struct folio *src, unsigned long private)
 {

mm/page_alloc.c

@@ -387,6 +387,24 @@ unsigned long get_pfnblock_flags_mask(const struct page *page,
 	word = READ_ONCE(bitmap[word_bitidx]);
 	return (word >> bitidx) & 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(const struct page *page,
 					unsigned long pfn)