1 files changed, 24 insertions, 26 deletions

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 31a848485ad9..2c3718d592d6 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -513,39 +513,37 @@ static inline bool mapping_large_folio_support(const struct address_space *mappi
 	return mapping_max_folio_order(mapping) > 0;
 }
 
-/* Return the maximum folio size for this pagecache mapping, in bytes. */
-static inline size_t mapping_max_folio_size(const struct address_space *mapping)
+/**
+ * mapping_pmd_folio_support() - Check if a mapping supports PMD-sized folio
+ * @mapping: The address_space
+ *
+ * While some mappings support large folios, they might not support PMD-sized
+ * folios. This function checks whether a mapping supports PMD-sized folios.
+ * For example, khugepaged needs this information before attempting to
+ * collapsing THPs.
+ *
+ * Return: True if PMD-sized folios are supported, otherwise false.
+ */
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static inline bool mapping_pmd_folio_support(const struct address_space *mapping)
 {
-	return PAGE_SIZE << mapping_max_folio_order(mapping);
-}
+	/* AS_FOLIO_ORDER is only reasonable for pagecache folios */
+	VM_WARN_ON_ONCE((unsigned long)mapping & FOLIO_MAPPING_ANON);
 
-static inline int filemap_nr_thps(const struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
-	return atomic_read(&mapping->nr_thps);
-#else
-	return 0;
-#endif
+	return mapping_min_folio_order(mapping) <= PMD_ORDER &&
+	       mapping_max_folio_order(mapping) >= PMD_ORDER;
 }
-
-static inline void filemap_nr_thps_inc(struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
-	if (!mapping_large_folio_support(mapping))
-		atomic_inc(&mapping->nr_thps);
 #else
-	WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0);
-#endif
+static inline bool mapping_pmd_folio_support(const struct address_space *mapping)
+{
+	return false;
 }
+#endif
 
-static inline void filemap_nr_thps_dec(struct address_space *mapping)
+/* Return the maximum folio size for this pagecache mapping, in bytes. */
+static inline size_t mapping_max_folio_size(const struct address_space *mapping)
 {
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
-	if (!mapping_large_folio_support(mapping))
-		atomic_dec(&mapping->nr_thps);
-#else
-	WARN_ON_ONCE(mapping_large_folio_support(mapping) == 0);
-#endif
+	return PAGE_SIZE << mapping_max_folio_order(mapping);
 }
 
 struct address_space *folio_mapping(const struct folio *folio);