pgtable: fix s390 ptdesc field comments

[ Upstream commit 38ca8a1 ]

Patch series "minor ptdesc updates", v3.

This patch (of 2):

Since commit d08d4e7 ("s390/mm: use full 4KB page for 2KB PTE") there
is no fragmented page tracking on s390.  Fix the corresponding comments.

Link: https://lkml.kernel.org/r/cover.1700594815.git.agordeev@linux.ibm.com
Link: https://lkml.kernel.org/r/2eead241f3a45bed26c7911cf66bded1e35670b8.1700594815.git.agordeev@linux.ibm.com
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Suggested-by: Heiko Carstens <hca@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: 59d9094 ("mm: hugetlb: independent PMD page table shared count")
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Alexander Gordeev

include/linux/mm_types.h

@@ -398,11 +398,11 @@ FOLIO_MATCH(compound_head, _head_2a);
  * @pmd_huge_pte:     Protected by ptdesc->ptl, used for THPs.
  * @__page_mapping:   Aliases with page->mapping. Unused for page tables.
  * @pt_mm:            Used for x86 pgds.
- * @pt_frag_refcount: For fragmented page table tracking. Powerpc and s390 only.
+ * @pt_frag_refcount: For fragmented page table tracking. Powerpc only.
  * @_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. Used for s390 page tables.
+ * @_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