v4.19.13 snapshot.
diff --git a/include/linux/compaction.h b/include/linux/compaction.h
new file mode 100644
index 0000000..68250a5
--- /dev/null
+++ b/include/linux/compaction.h
@@ -0,0 +1,247 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_COMPACTION_H
+#define _LINUX_COMPACTION_H
+
+/*
+ * Determines how hard direct compaction should try to succeed.
+ * Lower value means higher priority, analogically to reclaim priority.
+ */
+enum compact_priority {
+ COMPACT_PRIO_SYNC_FULL,
+ MIN_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_FULL,
+ COMPACT_PRIO_SYNC_LIGHT,
+ MIN_COMPACT_COSTLY_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
+ DEF_COMPACT_PRIORITY = COMPACT_PRIO_SYNC_LIGHT,
+ COMPACT_PRIO_ASYNC,
+ INIT_COMPACT_PRIORITY = COMPACT_PRIO_ASYNC
+};
+
+/* Return values for compact_zone() and try_to_compact_pages() */
+/* When adding new states, please adjust include/trace/events/compaction.h */
+enum compact_result {
+ /* For more detailed tracepoint output - internal to compaction */
+ COMPACT_NOT_SUITABLE_ZONE,
+ /*
+ * compaction didn't start as it was not possible or direct reclaim
+ * was more suitable
+ */
+ COMPACT_SKIPPED,
+ /* compaction didn't start as it was deferred due to past failures */
+ COMPACT_DEFERRED,
+
+ /* compaction not active last round */
+ COMPACT_INACTIVE = COMPACT_DEFERRED,
+
+ /* For more detailed tracepoint output - internal to compaction */
+ COMPACT_NO_SUITABLE_PAGE,
+ /* compaction should continue to another pageblock */
+ COMPACT_CONTINUE,
+
+ /*
+ * The full zone was compacted scanned but wasn't successfull to compact
+ * suitable pages.
+ */
+ COMPACT_COMPLETE,
+ /*
+ * direct compaction has scanned part of the zone but wasn't successfull
+ * to compact suitable pages.
+ */
+ COMPACT_PARTIAL_SKIPPED,
+
+ /* compaction terminated prematurely due to lock contentions */
+ COMPACT_CONTENDED,
+
+ /*
+ * direct compaction terminated after concluding that the allocation
+ * should now succeed
+ */
+ COMPACT_SUCCESS,
+};
+
+struct alloc_context; /* in mm/internal.h */
+
+/*
+ * Number of free order-0 pages that should be available above given watermark
+ * to make sure compaction has reasonable chance of not running out of free
+ * pages that it needs to isolate as migration target during its work.
+ */
+static inline unsigned long compact_gap(unsigned int order)
+{
+ /*
+ * Although all the isolations for migration are temporary, compaction
+ * free scanner may have up to 1 << order pages on its list and then
+ * try to split an (order - 1) free page. At that point, a gap of
+ * 1 << order might not be enough, so it's safer to require twice that
+ * amount. Note that the number of pages on the list is also
+ * effectively limited by COMPACT_CLUSTER_MAX, as that's the maximum
+ * that the migrate scanner can have isolated on migrate list, and free
+ * scanner is only invoked when the number of isolated free pages is
+ * lower than that. But it's not worth to complicate the formula here
+ * as a bigger gap for higher orders than strictly necessary can also
+ * improve chances of compaction success.
+ */
+ return 2UL << order;
+}
+
+#ifdef CONFIG_COMPACTION
+extern int sysctl_compact_memory;
+extern int sysctl_compaction_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos);
+extern int sysctl_extfrag_threshold;
+extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
+ void __user *buffer, size_t *length, loff_t *ppos);
+extern int sysctl_compact_unevictable_allowed;
+
+extern int fragmentation_index(struct zone *zone, unsigned int order);
+extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
+ unsigned int order, unsigned int alloc_flags,
+ const struct alloc_context *ac, enum compact_priority prio);
+extern void reset_isolation_suitable(pg_data_t *pgdat);
+extern enum compact_result compaction_suitable(struct zone *zone, int order,
+ unsigned int alloc_flags, int classzone_idx);
+
+extern void defer_compaction(struct zone *zone, int order);
+extern bool compaction_deferred(struct zone *zone, int order);
+extern void compaction_defer_reset(struct zone *zone, int order,
+ bool alloc_success);
+extern bool compaction_restarting(struct zone *zone, int order);
+
+/* Compaction has made some progress and retrying makes sense */
+static inline bool compaction_made_progress(enum compact_result result)
+{
+ /*
+ * Even though this might sound confusing this in fact tells us
+ * that the compaction successfully isolated and migrated some
+ * pageblocks.
+ */
+ if (result == COMPACT_SUCCESS)
+ return true;
+
+ return false;
+}
+
+/* Compaction has failed and it doesn't make much sense to keep retrying. */
+static inline bool compaction_failed(enum compact_result result)
+{
+ /* All zones were scanned completely and still not result. */
+ if (result == COMPACT_COMPLETE)
+ return true;
+
+ return false;
+}
+
+/*
+ * Compaction has backed off for some reason. It might be throttling or
+ * lock contention. Retrying is still worthwhile.
+ */
+static inline bool compaction_withdrawn(enum compact_result result)
+{
+ /*
+ * Compaction backed off due to watermark checks for order-0
+ * so the regular reclaim has to try harder and reclaim something.
+ */
+ if (result == COMPACT_SKIPPED)
+ return true;
+
+ /*
+ * If compaction is deferred for high-order allocations, it is
+ * because sync compaction recently failed. If this is the case
+ * and the caller requested a THP allocation, we do not want
+ * to heavily disrupt the system, so we fail the allocation
+ * instead of entering direct reclaim.
+ */
+ if (result == COMPACT_DEFERRED)
+ return true;
+
+ /*
+ * If compaction in async mode encounters contention or blocks higher
+ * priority task we back off early rather than cause stalls.
+ */
+ if (result == COMPACT_CONTENDED)
+ return true;
+
+ /*
+ * Page scanners have met but we haven't scanned full zones so this
+ * is a back off in fact.
+ */
+ if (result == COMPACT_PARTIAL_SKIPPED)
+ return true;
+
+ return false;
+}
+
+
+bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
+ int alloc_flags);
+
+extern int kcompactd_run(int nid);
+extern void kcompactd_stop(int nid);
+extern void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx);
+
+#else
+static inline void reset_isolation_suitable(pg_data_t *pgdat)
+{
+}
+
+static inline enum compact_result compaction_suitable(struct zone *zone, int order,
+ int alloc_flags, int classzone_idx)
+{
+ return COMPACT_SKIPPED;
+}
+
+static inline void defer_compaction(struct zone *zone, int order)
+{
+}
+
+static inline bool compaction_deferred(struct zone *zone, int order)
+{
+ return true;
+}
+
+static inline bool compaction_made_progress(enum compact_result result)
+{
+ return false;
+}
+
+static inline bool compaction_failed(enum compact_result result)
+{
+ return false;
+}
+
+static inline bool compaction_withdrawn(enum compact_result result)
+{
+ return true;
+}
+
+static inline int kcompactd_run(int nid)
+{
+ return 0;
+}
+static inline void kcompactd_stop(int nid)
+{
+}
+
+static inline void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx)
+{
+}
+
+#endif /* CONFIG_COMPACTION */
+
+#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
+struct node;
+extern int compaction_register_node(struct node *node);
+extern void compaction_unregister_node(struct node *node);
+
+#else
+
+static inline int compaction_register_node(struct node *node)
+{
+ return 0;
+}
+
+static inline void compaction_unregister_node(struct node *node)
+{
+}
+#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */
+
+#endif /* _LINUX_COMPACTION_H */