[PATCH 6.18.y 1/3] filemap: Add folio_next_pos()

[Sasha Levin <sashal@kernel.org>]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

[ Upstream commit 4511fd86db6f8f94f8aff01044f5c69aa38f81f4 ]

Replace the open-coded implementation in ocfs2 (which loses the top
32 bits on 32-bit architectures) with a helper in pagemap.h.

Fixes: 35edec1d52c0 (ocfs2: update truncate handling of partial clusters)
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://patch.msgid.link/20251024170822.1427218-2-willy@infradead.org
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: ocfs2-devel@lists.linux.dev
Signed-off-by: Christian Brauner <brauner@kernel.org>
Stable-dep-of: 329750292e9d ("xfarray: don't crash when sorting if array element crosses a folio")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/ocfs2/alloc.c        |  2 +-
 include/linux/pagemap.h | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index fb7d8dc2129be..d22ad99c9ebee 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -6891,7 +6891,7 @@ static void ocfs2_zero_cluster_folios(struct inode *inode, loff_t start,
 		ocfs2_map_and_dirty_folio(inode, handle, from, to, folio, 1,
 				&phys);
 
-		start = folio_next_index(folio) << PAGE_SHIFT;
+		start = folio_next_pos(folio);
 	}
 out:
 	if (folios)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 09b581c1d878d..e16576e3763a1 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -941,6 +941,17 @@ static inline pgoff_t folio_next_index(const struct folio *folio)
 	return folio->index + folio_nr_pages(folio);
 }
 
+/**
+ * folio_next_pos - Get the file position of the next folio.
+ * @folio: The current folio.
+ *
+ * Return: The position of the folio which follows this folio in the file.
+ */
+static inline loff_t folio_next_pos(const struct folio *folio)
+{
+	return (loff_t)folio_next_index(folio) << PAGE_SHIFT;
+}
+
 /**
  * folio_file_page - The page for a particular index.
  * @folio: The folio which contains this index.
-- 
2.53.0