mm/damon: move migration helpers from paddr to ops-common

This patch moves the damon_pa_migrate_pages function along with its
corresponding helper functions from paddr to ops-common.  The function
prefix of "damon_pa_" was also changed to just "damon_" accordingly.

This patch will allow page migration to be available to vaddr schemes as
well as paddr schemes.

Link: https://lkml.kernel.org/r/20250709005952.17776-9-bijan311@gmail.com
Co-developed-by: Ravi Shankar Jonnalagadda <ravis.opensrc@micron.com>
Signed-off-by: Ravi Shankar Jonnalagadda <ravis.opensrc@micron.com>
Signed-off-by: Bijan Tabatabai <bijantabatab@micron.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 120 insertions, 0 deletions

diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index b43620fee6bb..918158ef3d99 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -5,6 +5,7 @@
  * Author: SeongJae Park <sj@kernel.org>
  */
 
+#include <linux/migrate.h>
 #include <linux/mmu_notifier.h>
 #include <linux/page_idle.h>
 #include <linux/pagemap.h>
@@ -12,6 +13,7 @@
 #include <linux/swap.h>
 #include <linux/swapops.h>
 
+#include "../internal.h"
 #include "ops-common.h"
 
 /*
@@ -138,3 +140,121 @@ int damon_cold_score(struct damon_ctx *c, struct damon_region *r,
 	/* Return coldness of the region */
 	return DAMOS_MAX_SCORE - hotness;
 }
+
+static unsigned int __damon_migrate_folio_list(
+		struct list_head *migrate_folios, struct pglist_data *pgdat,
+		int target_nid)
+{
+	unsigned int nr_succeeded = 0;
+	struct migration_target_control mtc = {
+		/*
+		 * Allocate from 'node', or fail quickly and quietly.
+		 * When this happens, 'page' will likely just be discarded
+		 * instead of migrated.
+		 */
+		.gfp_mask = (GFP_HIGHUSER_MOVABLE & ~__GFP_RECLAIM) |
+			__GFP_NOWARN | __GFP_NOMEMALLOC | GFP_NOWAIT,
+		.nid = target_nid,
+	};
+
+	if (pgdat->node_id == target_nid || target_nid == NUMA_NO_NODE)
+		return 0;
+
+	if (list_empty(migrate_folios))
+		return 0;
+
+	/* Migration ignores all cpuset and mempolicy settings */
+	migrate_pages(migrate_folios, alloc_migration_target, NULL,
+		      (unsigned long)&mtc, MIGRATE_ASYNC, MR_DAMON,
+		      &nr_succeeded);
+
+	return nr_succeeded;
+}
+
+static unsigned int damon_migrate_folio_list(struct list_head *folio_list,
+						struct pglist_data *pgdat,
+						int target_nid)
+{
+	unsigned int nr_migrated = 0;
+	struct folio *folio;
+	LIST_HEAD(ret_folios);
+	LIST_HEAD(migrate_folios);
+
+	while (!list_empty(folio_list)) {
+		struct folio *folio;
+
+		cond_resched();
+
+		folio = lru_to_folio(folio_list);
+		list_del(&folio->lru);
+
+		if (!folio_trylock(folio))
+			goto keep;
+
+		/* Relocate its contents to another node. */
+		list_add(&folio->lru, &migrate_folios);
+		folio_unlock(folio);
+		continue;
+keep:
+		list_add(&folio->lru, &ret_folios);
+	}
+	/* 'folio_list' is always empty here */
+
+	/* Migrate folios selected for migration */
+	nr_migrated += __damon_migrate_folio_list(
+			&migrate_folios, pgdat, target_nid);
+	/*
+	 * Folios that could not be migrated are still in @migrate_folios.  Add
+	 * those back on @folio_list
+	 */
+	if (!list_empty(&migrate_folios))
+		list_splice_init(&migrate_folios, folio_list);
+
+	try_to_unmap_flush();
+
+	list_splice(&ret_folios, folio_list);
+
+	while (!list_empty(folio_list)) {
+		folio = lru_to_folio(folio_list);
+		list_del(&folio->lru);
+		folio_putback_lru(folio);
+	}
+
+	return nr_migrated;
+}
+
+unsigned long damon_migrate_pages(struct list_head *folio_list, int target_nid)
+{
+	int nid;
+	unsigned long nr_migrated = 0;
+	LIST_HEAD(node_folio_list);
+	unsigned int noreclaim_flag;
+
+	if (list_empty(folio_list))
+		return nr_migrated;
+
+	noreclaim_flag = memalloc_noreclaim_save();
+
+	nid = folio_nid(lru_to_folio(folio_list));
+	do {
+		struct folio *folio = lru_to_folio(folio_list);
+
+		if (nid == folio_nid(folio)) {
+			list_move(&folio->lru, &node_folio_list);
+			continue;
+		}
+
+		nr_migrated += damon_migrate_folio_list(&node_folio_list,
+							   NODE_DATA(nid),
+							   target_nid);
+		nid = folio_nid(lru_to_folio(folio_list));
+	} while (!list_empty(folio_list));
+
+	nr_migrated += damon_migrate_folio_list(&node_folio_list,
+						   NODE_DATA(nid),
+						   target_nid);
+
+	memalloc_noreclaim_restore(noreclaim_flag);
+
+	return nr_migrated;
+}