mm/migrate: don't call folio_putback_active_hugetlb() on dst hugetlb folio

We replaced a simple put_page() by a putback_active_hugepage() call in
commit 3aaa76e125c1 ("mm: migrate: hugetlb: putback destination hugepage
to active list"), to set the "active" flag on the dst hugetlb folio.

Nowadays, we decoupled the "active" list from the flag, by calling the
flag "migratable".

Calling "putback" on something that wasn't allocated is weird and not
future proof, especially if we might reach that path when migration failed
and we just want to free the freshly allocated hugetlb folio.

Let's simply handle the migratable flag and the active list flag in
move_hugetlb_state(), where we know that allocation succeeded and already
handle the temporary flag; use a simple folio_put() to return our
reference.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Reviewed-by: Baolin Wang <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Sidhartha Kumar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 10 insertions, 0 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 15a689964265..4f95031eeeea 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7533,6 +7533,16 @@ void move_hugetlb_state(struct folio *old_folio, struct folio *new_folio, int re
 		}
 		spin_unlock_irq(&hugetlb_lock);
 	}
+
+	/*
+	 * Our old folio is isolated and has "migratable" cleared until it
+	 * is putback. As migration succeeded, set the new folio "migratable"
+	 * and add it to the active list.
+	 */
+	spin_lock_irq(&hugetlb_lock);
+	folio_set_hugetlb_migratable(new_folio);
+	list_move_tail(&new_folio->lru, &(folio_hstate(new_folio))->hugepage_activelist);
+	spin_unlock_irq(&hugetlb_lock);
 }
 
 static void hugetlb_unshare_pmds(struct vm_area_struct *vma,