[PATCH 1/4] mm/damon: defensively skip zone device folios in damon_get_folio()

[Gregory Price]

All DAMON physical- and virtual-address operations obtain their folios
through damon_get_folio(). That helper already excludes ZONE_DEVICE
memory implicitly via pfn_to_online_page() and folio_test_lru(), but
this is inconsistent with other callers in mm/ which test explicitly.

Add an explicit folio_is_zone_device() rejection in damon_get_folio()
so the guarantee lives in one place and covers every caller uniformly,
consistent with other mm walkers that reject zone device folios.

Signed-off-by: Gregory Price (Meta) <gourry@xxxxxxxxxx>
---
 mm/damon/ops-common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index d7d7f100389b..d8bca7355b4f 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -32,7 +32,8 @@ struct folio *damon_get_folio(unsigned long pfn)
 	folio = page_folio(page);
 	if (!folio_try_get(folio))
 		return NULL;
-	if (unlikely(page_folio(page) != folio) || !folio_test_lru(folio)) {
+	if (unlikely(page_folio(page) != folio) || !folio_test_lru(folio) ||
+	    folio_is_zone_device(folio)) {
 		folio_put(folio);
 		folio = NULL;
 	}
-- 
2.55.0