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Date:   Tue,  6 Jun 2023 19:03:47 +0000
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Subject: [RFC PATCH 02/19] mm: hugetlb: Move and expose hugetlbfs_zero_partial_page
From:   Ackerley Tng <ackerleytng@google.com>
To:     akpm@linux-foundation.org, mike.kravetz@oracle.com,
        muchun.song@linux.dev, pbonzini@redhat.com, seanjc@google.com,
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        Ackerley Tng <ackerleytng@google.com>
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Precedence: bulk

Zeroing of pages is generalizable to hugetlb and is not specific to
hugetlbfs.

Rename hugetlbfs_zero_partial_page => hugetlb_zero_partial_page, move
it to mm/hugetlb.c and expose it in linux/hugetlb.h.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 fs/hugetlbfs/inode.c    | 27 ++-------------------------
 include/linux/hugetlb.h |  6 ++++++
 mm/hugetlb.c            | 22 ++++++++++++++++++++++
 3 files changed, 30 insertions(+), 25 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 406d7366cf3e..3dab50d3ed88 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -688,29 +688,6 @@ 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_folio(mapping, idx);
-	if (!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);
@@ -737,7 +714,7 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
 
 	/* If range starts before first full page, zero partial page. */
 	if (offset < hole_start)
-		hugetlbfs_zero_partial_page(h, mapping,
+		hugetlb_zero_partial_page(h, mapping,
 				offset, min(offset + len, hole_start));
 
 	/* Unmap users of full pages in the hole. */
@@ -750,7 +727,7 @@ 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,
+		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 37c2edf7beea..023293ceec25 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -256,6 +256,9 @@ long hugetlb_change_protection(struct vm_area_struct *vma,
 bool is_hugetlb_entry_migration(pte_t pte);
 void hugetlb_unshare_all_pmds(struct vm_area_struct *vma);
 
+void hugetlb_zero_partial_page(struct hstate *h, struct address_space *mapping,
+			       loff_t start, loff_t end);
+
 #else /* !CONFIG_HUGETLB_PAGE */
 
 static inline void hugetlb_dup_vma_private(struct vm_area_struct *vma)
@@ -464,6 +467,9 @@ static inline vm_fault_t hugetlb_fault(struct mm_struct *mm,
 
 static inline void hugetlb_unshare_all_pmds(struct vm_area_struct *vma) { }
 
+static inline void hugetlb_zero_partial_page(
+	struct hstate *h, struct address_space *mapping, loff_t start, loff_t end) {}
+
 #endif /* !CONFIG_HUGETLB_PAGE */
 /*
  * hugepages at page global directory. If arch support
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 07abcb6eb203..9c9262833b4f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -7407,6 +7407,28 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
 			ALIGN_DOWN(vma->vm_end, PUD_SIZE));
 }
 
+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_folio(mapping, idx);
+	if (!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);
+}
+
 #ifdef CONFIG_CMA
 static bool cma_reserve_called __initdata;
 
-- 
2.41.0.rc0.172.g3f132b7071-goog