[PATCH 6.12.y] mm/damon/ops-common: putback folios on invalid migrate nid

[SJ Park <sj@kernel.org>]

From: liyouhong <liyouhong@kylinos.cn>

damon_pa_migrate() and damos_va_migrate() isolate folios into a local list
and then call damon_migrate_pages().  When target_nid is invalid
(including the scheme default NUMA_NO_NODE / -1), damon_migrate_pages()
returns early without putting the folios back to the LRU.

Callers then discard the list head while those folios remain isolated with
an extra reference taken by folio_isolate_lru().  The pages stay off the
LRU for as long as the mapping exists (anon active+inactive counts drop
while RSS does not), and the leftover references can pin the pages after
the mapping is gone.

Put the folios back on the invalid-nid path so ignored migration requests
still return them to the LRU.

Link: https://lore.kernel.org/20260726014815.1280757-1-dayou5941@163.com
Fixes: 7e6c3130690a ("mm/damon/ops-common: ignore migration request to invalid nodes")
Assisted-by: Cursor:grok-4.5
Reviewed-by: SJ Park <sj@kernel.org>
Signed-off-by: liyouhong <liyouhong@kylinos.cn>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 5deb65c34e682e7c5f5df417a70e223e8fcc5f5a)
Signed-off-by: SJ Park <sj@kernel.org>
---
 mm/damon/paddr.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 4120a73f49339..884042856f7ea 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -432,8 +432,15 @@ static unsigned long damon_pa_migrate_pages(struct list_head *folio_list,
 		return nr_migrated;
 
 	if (target_nid < 0 || target_nid >= MAX_NUMNODES ||
-			!node_state(target_nid, N_MEMORY))
+			!node_state(target_nid, N_MEMORY)) {
+		while (!list_empty(folio_list)) {
+			struct folio *folio = lru_to_folio(folio_list);
+
+			list_del(&folio->lru);
+			folio_putback_lru(folio);
+		}
 		return nr_migrated;
+	}
 
 	noreclaim_flag = memalloc_noreclaim_save();
 
-- 
2.47.3