pgtable: rename ptdesc _refcount field to __page_refcount

Rename ptdesc _refcount field to __page_refcount similar to the other
unused page fields.

Link: https://lkml.kernel.org/r/982bdc652ba79a606c3d01c905766e7e076b3315.1700594815.git.agordeev@linux.ibm.comSigned-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Suggested-by: Vishal Moola <vishal.moola@gmail.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

include/linux/mm_types.h

@@ -405,7 +405,7 @@ FOLIO_MATCH(compound_head, _head_2a);
  * @_pt_pad_2:        Padding to ensure proper alignment.
  * @ptl:              Lock for the page table.
  * @__page_type:      Same as page->page_type. Unused for page tables.
- * @_refcount:        Same as page refcount.
+ * @__page_refcount:  Same as page refcount.
  * @pt_memcg_data:    Memcg data. Tracked for page tables here.
  *
  * This struct overlays struct page for now. Do not modify without a good
@@ -438,7 +438,7 @@ struct ptdesc {
 #endif
 	};
 	unsigned int __page_type;
-	atomic_t _refcount;
+	atomic_t __page_refcount;
 #ifdef CONFIG_MEMCG
 	unsigned long pt_memcg_data;
 #endif
@@ -452,7 +452,7 @@ TABLE_MATCH(compound_head, _pt_pad_1);
 TABLE_MATCH(mapping, __page_mapping);
 TABLE_MATCH(rcu_head, pt_rcu_head);
 TABLE_MATCH(page_type, __page_type);
-TABLE_MATCH(_refcount, _refcount);
+TABLE_MATCH(_refcount, __page_refcount);
 #ifdef CONFIG_MEMCG
 TABLE_MATCH(memcg_data, pt_memcg_data);
 #endif