On 13.08.25 07:05, Lance Yang wrote:

On Mon, Aug 11, 2025 at 10:47 PM David Hildenbrand [off-list ref] wrote:

quoted

[...]

quoted

+++ b/mm/migrate.c

@@ -1176,16 +1176,6 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,
         bool locked = false;
         bool dst_locked = false;

-       if (folio_ref_count(src) == 1) {
-               /* Folio was freed from under us. So we are done. */
-               folio_clear_active(src);
-               folio_clear_unevictable(src);
-               /* free_pages_prepare() will clear PG_isolated. */
-               list_del(&src->lru);
-               migrate_folio_done(src, reason);
-               return MIGRATEPAGE_SUCCESS;
-       }
-
         dst = get_new_folio(src, private);
         if (!dst)
                 return -ENOMEM;

@@ -1275,7 +1265,7 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,

         if (unlikely(page_has_movable_ops(&src->page))) {
                 __migrate_folio_record(dst, old_page_state, anon_vma);
-               return MIGRATEPAGE_UNMAP;
+               return 0;
         }

         /*

@@ -1305,7 +1295,7 @@ static int migrate_folio_unmap(new_folio_t get_new_folio,

         if (!folio_mapped(src)) {
                 __migrate_folio_record(dst, old_page_state, anon_vma);
-               return MIGRATEPAGE_UNMAP;
+               return 0;
         }

  out:

@@ -1848,14 +1838,28 @@ static int migrate_pages_batch(struct list_head *from,
                                 continue;
                         }

+                       /*
+                        * If we are holding the last folio reference, the folio
+                        * was freed from under us, so just drop our reference.
+                        */
+                       if (likely(!page_has_movable_ops(&folio->page)) &&
+                           folio_ref_count(folio) == 1) {
+                               folio_clear_active(folio);
+                               folio_clear_unevictable(folio);
+                               list_del(&folio->lru);
+                               migrate_folio_done(folio, reason);
+                               stats->nr_succeeded += nr_pages;
+                               stats->nr_thp_succeeded += is_thp;
+                               continue;
+                       }
+

It seems the reason parameter is no longer used within migrate_folio_unmap()
after this patch.

Perhaps it could be removed from the function's signature ;)

Thanks, well spotted, @Andrew can you squash the following?


 From 40938bb0de20e03250c813d5abc7286aea69d835 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <redacted>
Date: Mon, 18 Aug 2025 13:26:05 +0200
Subject: [PATCH] fixup: mm/migrate: remove MIGRATEPAGE_UNMAP

No need to pass "reason" to migrate_folio_unmap().

Signed-off-by: David Hildenbrand <redacted>
---
  mm/migrate.c | 5 ++---
  1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index 2db4974178e6a..aabc736eec022 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c

@@ -1166,7 +1166,7 @@ static void migrate_folio_done(struct folio *src,
  static int migrate_folio_unmap(new_folio_t get_new_folio,
  		free_folio_t put_new_folio, unsigned long private,
  		struct folio *src, struct folio **dstp, enum migrate_mode mode,
-		enum migrate_reason reason, struct list_head *ret)
+		struct list_head *ret)
  {
  	struct folio *dst;
  	int rc = -EAGAIN;

@@ -1852,8 +1852,7 @@ static int migrate_pages_batch(struct list_head *from,
  			}
  
  			rc = migrate_folio_unmap(get_new_folio, put_new_folio,
-					private, folio, &dst, mode, reason,
-					ret_folios);
+					private, folio, &dst, mode, ret_folios);
  			/*
  			 * The rules are:
  			 *	0: folio will be put on unmap_folios list,

-- 
2.50.1


-- 
Cheers

David / dhildenb