These functions are introduced in hugetlb.c so the private
hugetlb_lock can be accessed.

hugetlb_lock is reused for this PoC, but a separate lock should be
used in a future revision to avoid interference due to hash collisions
with HugeTLB's usage of this lock.

Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Co-developed-by: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>

---
 include/linux/hugetlb.h |  3 +++
 mm/hugetlb.c            | 21 +++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index ac9d4ada52bd..0f3f920ad608 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -164,6 +164,9 @@ bool hugetlb_reserve_pages(struct inode *inode, long from, long to,
 						vm_flags_t vm_flags);
 long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
 						long freed);
+void hugetlb_folio_list_add(struct folio *folio, struct list_head *list);
+void hugetlb_folio_list_move(struct folio *folio, struct list_head *list);
+void hugetlb_folio_list_del(struct folio *folio);
 bool isolate_hugetlb(struct folio *folio, struct list_head *list);
 int get_hwpoison_hugetlb_folio(struct folio *folio, bool *hugetlb, bool unpoison);
 int get_huge_page_for_hwpoison(unsigned long pfn, int flags,
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8f2b7b411b60..60e72214d5bf 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7264,6 +7264,27 @@ long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
 	return 0;
 }
 
+void hugetlb_folio_list_add(struct folio *folio, struct list_head *list)
+{
+	spin_lock_irq(&hugetlb_lock);
+	list_add(&folio->lru, list);
+	spin_unlock_irq(&hugetlb_lock);
+}
+
+void hugetlb_folio_list_move(struct folio *folio, struct list_head *list)
+{
+	spin_lock_irq(&hugetlb_lock);
+	list_move_tail(&folio->lru, list);
+	spin_unlock_irq(&hugetlb_lock);
+}
+
+void hugetlb_folio_list_del(struct folio *folio)
+{
+	spin_lock_irq(&hugetlb_lock);
+	list_del(&folio->lru);
+	spin_unlock_irq(&hugetlb_lock);
+}
+
 #ifdef CONFIG_ARCH_WANT_HUGE_PMD_SHARE
 static unsigned long page_table_shareable(struct vm_area_struct *svma,
 				struct vm_area_struct *vma,
-- 
2.46.0.598.g6f2099f65c-goog