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/20260714015117.78351-4-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>
Acked-by: David Hildenbrand (Arm) <david@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>

1 files changed, 5 insertions, 4 deletions

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2abaf99321e9..d6967fc94a49 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;
 }