[PATCH 14/15] mm/page_owner, alloc_tag: use folio_page() for page_ext and codetag

[Nilay Vaish]

As part of the memdescs effort, struct folio will be allocated
separately from struct page and will no longer overlay the head page.

Replace direct &folio->page, &old->page, &new->page, and &newfolio->page
uses with folio_page(..., 0) in __folio_set_owner_migrate_reason(),
__folio_copy_owner(), pgalloc_tag_split(), and pgalloc_tag_swap().

No functional change intended.

Assisted-by: LLM
Signed-off-by: Nilay Vaish <nilayvaish@xxxxxxxxxx>
---
 mm/alloc_tag.c  | 10 +++++-----
 mm/page_owner.c | 15 +++++++++------
 2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c
index 82e2c3448dcf..c93efb224ce1 100644
--- a/mm/alloc_tag.c
+++ b/mm/alloc_tag.c
@@ -534,7 +534,7 @@ void pgalloc_tag_split(struct folio *folio, int old_order, int new_order)
 	if (!mem_alloc_profiling_enabled())
 		return;
 
-	tag = __pgalloc_tag_get(&folio->page);
+	tag = __pgalloc_tag_get(folio_page(folio, 0));
 	if (!tag)
 		return;
 
@@ -560,16 +560,16 @@ void pgalloc_tag_swap(struct folio *new, struct folio *old)
 	if (!mem_alloc_profiling_enabled())
 		return;
 
-	tag_old = __pgalloc_tag_get(&old->page);
+	tag_old = __pgalloc_tag_get(folio_page(old, 0));
 	if (!tag_old)
 		return;
-	tag_new = __pgalloc_tag_get(&new->page);
+	tag_new = __pgalloc_tag_get(folio_page(new, 0));
 	if (!tag_new)
 		return;
 
-	if (!get_page_tag_ref(&old->page, &ref_old, &handle_old))
+	if (!get_page_tag_ref(folio_page(old, 0), &ref_old, &handle_old))
 		return;
-	if (!get_page_tag_ref(&new->page, &ref_new, &handle_new)) {
+	if (!get_page_tag_ref(folio_page(new, 0), &ref_new, &handle_new)) {
 		put_page_tag_ref(handle_old);
 		return;
 	}
diff --git a/mm/page_owner.c b/mm/page_owner.c
index cfc31c92d765..39c381699a63 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -365,7 +365,7 @@ noinline void __set_page_owner(struct page *page, unsigned short order,
 
 void __folio_set_owner_migrate_reason(struct folio *folio, enum migrate_reason reason)
 {
-	struct page_ext *page_ext = page_ext_get(&folio->page);
+	struct page_ext *page_ext = page_ext_get(folio_page(folio, 0));
 	struct page_owner *page_owner;
 
 	if (unlikely(!page_ext))
@@ -398,14 +398,14 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old)
 	struct page_owner *new_page_owner;
 	depot_stack_handle_t migrate_handle;
 
-	page_ext = page_ext_get(&old->page);
+	page_ext = page_ext_get(folio_page(old, 0));
 	if (unlikely(!page_ext))
 		return;
 
 	old_page_owner = get_page_owner(page_ext);
 	page_ext_put(page_ext);
 
-	page_ext = page_ext_get(&newfolio->page);
+	page_ext = page_ext_get(folio_page(newfolio, 0));
 	if (unlikely(!page_ext))
 		return;
 
@@ -413,7 +413,8 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old)
 	page_ext_put(page_ext);
 
 	migrate_handle = new_page_owner->handle;
-	__update_page_owner_handle(&newfolio->page, old_page_owner->handle,
+	__update_page_owner_handle(folio_page(newfolio, 0),
+				   old_page_owner->handle,
 				   old_page_owner->order, old_page_owner->gfp_mask,
 				   old_page_owner->last_migrate_reason,
 				   old_page_owner->ts_nsec, old_page_owner->pid,
@@ -423,7 +424,8 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old)
 	 * will be freed after migration. Keep them until then as they may be
 	 * useful.
 	 */
-	__update_page_owner_free_handle(&newfolio->page, 0, old_page_owner->order,
+	__update_page_owner_free_handle(folio_page(newfolio, 0), 0,
+					old_page_owner->order,
 					old_page_owner->free_pid,
 					old_page_owner->free_tgid,
 					old_page_owner->free_ts_nsec);
@@ -433,7 +435,8 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old)
 	 * when subtracting those pages from the stack.
 	 */
 	rcu_read_lock();
-	for_each_page_ext(&old->page, 1 << new_page_owner->order, page_ext, iter) {
+	for_each_page_ext(folio_page(old, 0), 1 << new_page_owner->order,
+			  page_ext, iter) {
 		old_page_owner = get_page_owner(page_ext);
 		old_page_owner->handle = migrate_handle;
 	}
-- 
2.56.0.rc1.315.gc6ed9934b7-goog