* references the entire folio counts exactly once, even when such special
* page table entries are comprised of multiple ordinary page table entries.
*
+ * Will report 0 for pages which cannot be mapped into userspace, such as
+ * slab, page tables and similar.
+ *
* Return: The number of times this folio is mapped.
*/
static inline int folio_mapcount(const struct folio *folio)
{
- if (likely(!folio_test_large(folio)))
- return atomic_read(&folio->_mapcount) + 1;
+ int mapcount;
+
+ if (likely(!folio_test_large(folio))) {
+ mapcount = atomic_read(&folio->_mapcount) + 1;
+ /* Handle page_has_type() pages */
+ if (mapcount < PAGE_MAPCOUNT_RESERVE + 1)
+ mapcount = 0;
+ return mapcount;
+ }
return folio_large_mapcount(folio);
}