[PATCH v4 3/5] mm/hugetlb: add hugetlb_folio_subpool() helpers

[Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>]

Allows hugetlbfs_migrate_folio to check and read subpool information by
passing in a folio.

Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
 fs/hugetlbfs/inode.c    |  8 ++++----
 include/linux/hugetlb.h | 15 +++++++++++++--
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index ed57a029eab0..5a4b136c6c36 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -1099,10 +1099,10 @@ static int hugetlbfs_migrate_folio(struct address_space *mapping,
 	if (rc != MIGRATEPAGE_SUCCESS)
 		return rc;
 
-	if (hugetlb_page_subpool(&src->page)) {
-		hugetlb_set_page_subpool(&dst->page,
-					hugetlb_page_subpool(&src->page));
-		hugetlb_set_page_subpool(&src->page, NULL);
+	if (hugetlb_folio_subpool(src)) {
+		hugetlb_set_folio_subpool(dst,
+					hugetlb_folio_subpool(src));
+		hugetlb_set_folio_subpool(src, NULL);
 	}
 
 	if (mode != MIGRATE_SYNC_NO_COPY)
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 8edcdb6a833f..f92b9e6c8f9e 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -752,18 +752,29 @@ extern unsigned int default_hstate_idx;
 
 #define default_hstate (hstates[default_hstate_idx])
 
+static inline struct hugepage_subpool *hugetlb_folio_subpool(struct folio *folio)
+{
+	return (void *)folio_get_private_1(folio);
+}
+
 /*
  * hugetlb page subpool pointer located in hpage[1].private
  */
 static inline struct hugepage_subpool *hugetlb_page_subpool(struct page *hpage)
 {
-	return (void *)page_private(hpage + SUBPAGE_INDEX_SUBPOOL);
+	return hugetlb_folio_subpool(page_folio(hpage));
+}
+
+static inline void hugetlb_set_folio_subpool(struct folio *folio,
+					struct hugepage_subpool *subpool)
+{
+	folio_set_private_1(folio, (unsigned long)subpool);
 }
 
 static inline void hugetlb_set_page_subpool(struct page *hpage,
 					struct hugepage_subpool *subpool)
 {
-	set_page_private(hpage + SUBPAGE_INDEX_SUBPOOL, (unsigned long)subpool);
+	hugetlb_set_folio_subpool(page_folio(hpage), subpool);
 }
 
 static inline struct hstate *hstate_file(struct file *f)
-- 
2.31.1