This will used by guest_memfd in a later patch.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 fs/hugetlbfs/inode.c    | 33 +++++----------------------------
 include/linux/hugetlb.h |  3 +++
 mm/hugetlb.c            | 21 +++++++++++++++++++++
 3 files changed, 29 insertions(+), 28 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 300a6ef300c1..f76001418672 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -720,29 +720,6 @@ static void hugetlb_vmtruncate(struct inode *inode, loff_t offset)
 	remove_inode_hugepages(inode, offset, LLONG_MAX);
 }
 
-static void hugetlbfs_zero_partial_page(struct hstate *h,
-					struct address_space *mapping,
-					loff_t start,
-					loff_t end)
-{
-	pgoff_t idx = start >> huge_page_shift(h);
-	struct folio *folio;
-
-	folio = filemap_lock_hugetlb_folio(h, mapping, idx);
-	if (IS_ERR(folio))
-		return;
-
-	start = start & ~huge_page_mask(h);
-	end = end & ~huge_page_mask(h);
-	if (!end)
-		end = huge_page_size(h);
-
-	folio_zero_segment(folio, (size_t)start, (size_t)end);
-
-	folio_unlock(folio);
-	folio_put(folio);
-}
-
 static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 {
 	struct hugetlbfs_inode_info *info = HUGETLBFS_I(inode);
@@ -768,9 +745,10 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 	i_mmap_lock_write(mapping);
 
 	/* If range starts before first full page, zero partial page. */
-	if (offset < hole_start)
-		hugetlbfs_zero_partial_page(h, mapping,
-				offset, min(offset + len, hole_start));
+	if (offset < hole_start) {
+		hugetlb_zero_partial_page(h, mapping, offset,
+					  min(offset + len, hole_start));
+	}
 
 	/* Unmap users of full pages in the hole. */
 	if (hole_end > hole_start) {
@@ -782,8 +760,7 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 
 	/* If range extends beyond last full page, zero partial page. */
 	if ((offset + len) > hole_end && (offset + len) > hole_start)
-		hugetlbfs_zero_partial_page(h, mapping,
-				hole_end, offset + len);
+		hugetlb_zero_partial_page(h, mapping, hole_end, offset + len);
 
 	i_mmap_unlock_write(mapping);
 
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 4d47bf94c211..752062044b0b 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -124,6 +124,9 @@ long hugepage_subpool_put_pages(struct hugepage_subpool *spool, long delta);
 
 int hugetlb_acct_memory(struct hstate *h, long delta);
 
+void hugetlb_zero_partial_page(struct hstate *h, struct address_space *mapping,
+			       loff_t start, loff_t end);
+
 void hugetlb_dup_vma_private(struct vm_area_struct *vma);
 void clear_vma_resv_huge_pages(struct vm_area_struct *vma);
 int move_hugetlb_page_tables(struct vm_area_struct *vma,
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5a37b03e1361..372d8294fb2f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1989,6 +1989,27 @@ void free_huge_folio(struct folio *folio)
 	}
 }
 
+void hugetlb_zero_partial_page(struct hstate *h, struct address_space *mapping,
+			       loff_t start, loff_t end)
+{
+	pgoff_t idx = start >> huge_page_shift(h);
+	struct folio *folio;
+
+	folio = filemap_lock_hugetlb_folio(h, mapping, idx);
+	if (IS_ERR(folio))
+		return;
+
+	start = start & ~huge_page_mask(h);
+	end = end & ~huge_page_mask(h);
+	if (!end)
+		end = huge_page_size(h);
+
+	folio_zero_segment(folio, (size_t)start, (size_t)end);
+
+	folio_unlock(folio);
+	folio_put(folio);
+}
+
 /*
  * Must be called with the hugetlb lock held
  */
-- 
2.46.0.598.g6f2099f65c-goog