[PATCH 1/1] mm/rmap: add CONFIG_MM_ID guard for folio_test_large_maybe_mapped_shared()

[Lance Yang]

Add a compile-time check to make sure folio_test_large_maybe_mapped_shared()
is only used with CONFIG_MM_ID enabled, as it directly accesses the _mm_ids
field that only works under CONFIG_MM_ID.

Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Mingzhe Yang <mingzhe.yang@xxxxxx>
Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
---
 include/linux/page-flags.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index d3909cb1e576..6bd9b9043976 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -1232,6 +1232,8 @@ static inline int folio_has_private(const struct folio *folio)
 
 static inline bool folio_test_large_maybe_mapped_shared(const struct folio *folio)
 {
+	/* This function should never be called without CONFIG_MM_ID enabled. */
+	BUILD_BUG_ON(!IS_ENABLED(CONFIG_MM_ID));
 	return test_bit(FOLIO_MM_IDS_SHARED_BITNUM, &folio->_mm_ids);
 }
 #undef PF_ANY
-- 
2.49.0