mm: use enum migrate_reason instead of int for migration reason parameters

Replace all 'int reason' function parameters that carry migrate_reason
values with the proper 'enum migrate_reason' type.  This makes the intent
explicit and leverages compiler type checking.  The affected subsystems
are:

  - page_owner: __folio_set_owner_migrate_reason(),
                folio_set_owner_migrate_reason()
  - migrate: migrate_pages(), migrate_pages_sync(),
             migrate_pages_batch(), migrate_folios_move(),
             migrate_hugetlbs(), unmap_and_move_huge_page()
  - hugetlb: move_hugetlb_state(), htlb_allow_alloc_fallback()
  - trace: mm_migrate_pages and mm_migrate_pages_start events

The 'short last_migrate_reason' struct field and internal helper
parameter in page_owner are intentionally left as 'short' since they
store per-page metadata where size matters.

No functional change.

Link: https://lore.kernel.org/20260701061101.344679-4-ye.liu@linux.dev
Signed-off-by: Ye Liu <ye.liu@linux.dev>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

4 files changed, 17 insertions, 13 deletions

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2abaf99321e9..fa828232dfcc 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -154,7 +154,8 @@ long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
 bool folio_isolate_hugetlb(struct folio *folio, struct list_head *list);
 int get_hwpoison_hugetlb_folio(struct folio *folio, bool *hugetlb, bool unpoison);
 void folio_putback_hugetlb(struct folio *folio);
-void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int reason);
+void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio,
+			enum migrate_reason reason);
 void hugetlb_fix_reserve_counts(struct inode *inode);
 extern struct mutex *hugetlb_fault_mutex_table;
 u32 hugetlb_fault_mutex_hash(struct address_space *mapping, pgoff_t idx);
@@ -424,7 +425,7 @@ static inline void folio_putback_hugetlb(struct folio *folio)
 }
 
 static inline void move_hugetlb_state(struct folio *old_folio,
-					struct folio *new_folio, int reason)
+					struct folio *new_folio, enum migrate_reason reason)
 {
 }
 
@@ -956,7 +957,7 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
 	return modified_mask;
 }
 
-static inline bool htlb_allow_alloc_fallback(int reason)
+static inline bool htlb_allow_alloc_fallback(enum migrate_reason reason)
 {
 	bool allowed_fallback = false;
 
@@ -1238,7 +1239,7 @@ static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
 	return 0;
 }
 
-static inline bool htlb_allow_alloc_fallback(int reason)
+static inline bool htlb_allow_alloc_fallback(enum migrate_reason reason)
 {
 	return false;
 }
diff --git a/include/linux/migrate.h b/include/linux/migrate.h
index d5af2b7f577b..1f83924615d6 100644
--- a/include/linux/migrate.h
+++ b/include/linux/migrate.h
@@ -57,7 +57,8 @@ void putback_movable_pages(struct list_head *l);
 int migrate_folio(struct address_space *mapping, struct folio *dst,
 		struct folio *src, enum migrate_mode mode);
 int migrate_pages(struct list_head *l, new_folio_t new, free_folio_t free,
-		  unsigned long private, enum migrate_mode mode, int reason,
+		  unsigned long private, enum migrate_mode mode,
+		  enum migrate_reason reason,
 		  unsigned int *ret_succeeded);
 struct folio *alloc_migration_target(struct folio *src, unsigned long private);
 bool isolate_movable_ops_page(struct page *page, isolate_mode_t mode);
@@ -77,7 +78,8 @@ int set_movable_ops(const struct movable_operations *ops, enum pagetype type);
 static inline void putback_movable_pages(struct list_head *l) {}
 static inline int migrate_pages(struct list_head *l, new_folio_t new,
 		free_folio_t free, unsigned long private,
-		enum migrate_mode mode, int reason, unsigned int *ret_succeeded)
+		enum migrate_mode mode, enum migrate_reason reason,
+		unsigned int *ret_succeeded)
 	{ return -ENOSYS; }
 static inline struct folio *alloc_migration_target(struct folio *src,
 		unsigned long private)
diff --git a/include/linux/page_owner.h b/include/linux/page_owner.h
index 3328357f6dba..9fe51dfccf26 100644
--- a/include/linux/page_owner.h
+++ b/include/linux/page_owner.h
@@ -3,6 +3,7 @@
 #define __LINUX_PAGE_OWNER_H
 
 #include <linux/jump_label.h>
+#include <linux/migrate_mode.h>
 
 #ifdef CONFIG_PAGE_OWNER
 extern struct static_key_false page_owner_inited;
@@ -14,7 +15,7 @@ extern void __set_page_owner(struct page *page,
 extern void __split_page_owner(struct page *page, int old_order,
 			int new_order);
 extern void __folio_copy_owner(struct folio *newfolio, struct folio *old);
-extern void __folio_set_owner_migrate_reason(struct folio *folio, int reason);
+extern void __folio_set_owner_migrate_reason(struct folio *folio, enum migrate_reason reason);
 extern void __dump_page_owner(const struct page *page);
 extern void pagetypeinfo_showmixedcount_print(struct seq_file *m,
 					pg_data_t *pgdat, struct zone *zone);
@@ -43,7 +44,7 @@ static inline void folio_copy_owner(struct folio *newfolio, struct folio *old)
 	if (static_branch_unlikely(&page_owner_inited))
 		__folio_copy_owner(newfolio, old);
 }
-static inline void folio_set_owner_migrate_reason(struct folio *folio, int reason)
+static inline void folio_set_owner_migrate_reason(struct folio *folio, enum migrate_reason reason)
 {
 	if (static_branch_unlikely(&page_owner_inited))
 		__folio_set_owner_migrate_reason(folio, reason);
@@ -68,7 +69,7 @@ static inline void split_page_owner(struct page *page, int old_order,
 static inline void folio_copy_owner(struct folio *newfolio, struct folio *folio)
 {
 }
-static inline void folio_set_owner_migrate_reason(struct folio *folio, int reason)
+static inline void folio_set_owner_migrate_reason(struct folio *folio, enum migrate_reason reason)
 {
 }
 static inline void dump_page_owner(const struct page *page)
diff --git a/include/trace/events/migrate.h b/include/trace/events/migrate.h
index 11bc0aa14c7e..15ee2ef201b5 100644
--- a/include/trace/events/migrate.h
+++ b/include/trace/events/migrate.h
@@ -52,7 +52,7 @@ TRACE_EVENT(mm_migrate_pages,
 	TP_PROTO(unsigned long succeeded, unsigned long failed,
 		 unsigned long thp_succeeded, unsigned long thp_failed,
 		 unsigned long thp_split, unsigned long large_folio_split,
-		 enum migrate_mode mode, int reason),
+		 enum migrate_mode mode, enum migrate_reason reason),
 
 	TP_ARGS(succeeded, failed, thp_succeeded, thp_failed,
 		thp_split, large_folio_split, mode, reason),
@@ -65,7 +65,7 @@ TRACE_EVENT(mm_migrate_pages,
 		__field(	unsigned long,		thp_split)
 		__field(	unsigned long,		large_folio_split)
 		__field(	enum migrate_mode,	mode)
-		__field(	int,			reason)
+		__field(	enum migrate_reason,	reason)
 	),
 
 	TP_fast_assign(
@@ -92,13 +92,13 @@ TRACE_EVENT(mm_migrate_pages,
 
 TRACE_EVENT(mm_migrate_pages_start,
 
-	TP_PROTO(enum migrate_mode mode, int reason),
+	TP_PROTO(enum migrate_mode mode, enum migrate_reason reason),
 
 	TP_ARGS(mode, reason),
 
 	TP_STRUCT__entry(
 		__field(enum migrate_mode, mode)
-		__field(int, reason)
+		__field(enum migrate_reason, reason)
 	),
 
 	TP_fast_assign(