ksm: update comments and docs to reference folio->mapping

The KSM code already stores and checks the stable node key via
folio->mapping, but the comment in ksm_get_folio() and the reverse mapping
documentation in ksm.rst still refer to page->mapping.

This is a pure wording update to match the folio-based implementation.  No
functional change is intended.

Link: https://lore.kernel.org/20260805105927.41987-1-hongfu.li@linux.dev
Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Xu Xin <xu.xin16@zte.com.cn>
Reviewed-by: Dongliang Mu <dzm91@hust.edu.cn>
Cc: Alex Shi <alexs@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Yanteng Si <si.yanteng@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Documentation/mm/ksm.rst

@@ -24,13 +24,13 @@ tree.
 
 If a KSM page is shared between less than ``max_page_sharing`` VMAs,
 the node of the stable tree that represents such KSM page points to a
-list of struct ksm_rmap_item and the ``page->mapping`` of the
+list of struct ksm_rmap_item and the ``folio->mapping`` of the
 KSM page points to the stable tree node.
 
 When the sharing passes this threshold, KSM adds a second dimension to
 the stable tree. The tree node becomes a "chain" that links one or
 more "dups". Each "dup" keeps reverse mapping information for a KSM
-page with ``page->mapping`` pointing to that "dup".
+page with ``folio->mapping`` pointing to that "dup".
 
 Every "chain" and all "dups" linked into a "chain" enforce the
 invariant that they represent the same write protected memory content,

Documentation/translations/zh_CN/mm/ksm.rst

@@ -31,10 +31,10 @@ KSM维护着稳定树中的KSM页的逆映射信息。
 
 当KSM页面的共享数小于 ``max_page_sharing`` 的虚拟内存区域(VMAs)时，则代表了
 KSM页的稳定树其中的节点指向了一个ksm_rmap_item结构体类型的列表。同时，这个KSM页
-的 ``page->mapping`` 指向了该稳定树节点。
+的 ``folio->mapping`` 指向了该稳定树节点。
 
 如果共享数超过了阈值，KSM将给稳定树添加第二个维度。稳定树就变成链接一个或多
-个稳定树"副本"的"链"。每个副本都保留KSM页的逆映射信息，其中 ``page->mapping``
+个稳定树"副本"的"链"。每个副本都保留KSM页的逆映射信息，其中 ``folio->mapping``
 指向该"副本"。
 
 每个链以及链接到该链中的所有"副本"强制不变的是，它们代表了相同的写保护内存

mm/ksm.c

@@ -959,10 +959,9 @@ enum ksm_get_folio_flags {
  * seconds or even minutes: much too unresponsive.  So instead we use a
  * "keyhole reference": access to the ksm page from the stable node peeps
  * out through its keyhole to see if that page still holds the right key,
- * pointing back to this stable node.  This relies on freeing a PageAnon
- * page to reset its page->mapping to NULL, and relies on no other use of
- * a page to put something that might look like our key in page->mapping.
- * is on its way to being freed; but it is an anomaly to bear in mind.
+ * pointing back to this stable node.  This relies on freeing an anon
+ * folio to reset its mapping to NULL, and relies on no other use of a
+ * folio to put something that might look like our key in its mapping.
  */
 static struct folio *ksm_get_folio(struct ksm_stable_node *stable_node,
 				 enum ksm_get_folio_flags flags)