[RFC 1/4] fs/buffer: add set_bh_folio helper

[Pankaj Raghav <p.raghav@samsung.com>]

The folio version of set_bh_page(). This is required to convert
create_page_buffers() to create_folio_buffers() later in the series.

Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
 fs/buffer.c                 | 15 +++++++++++++++
 include/linux/buffer_head.h |  2 ++
 2 files changed, 17 insertions(+)

diff --git a/fs/buffer.c b/fs/buffer.c
index b3eb905f87d6..44380ff3a31f 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1484,6 +1484,21 @@ void set_bh_page(struct buffer_head *bh,
 }
 EXPORT_SYMBOL(set_bh_page);
 
+void set_bh_folio(struct buffer_head *bh, struct folio *folio,
+		  unsigned long offset)
+{
+	bh->b_folio = folio;
+	BUG_ON(offset >= folio_size(folio));
+	if (folio_test_highmem(folio))
+		/*
+		 * This catches illegal uses and preserves the offset:
+		 */
+		bh->b_data = (char *)(0 + offset);
+	else
+		bh->b_data = folio_address(folio) + offset;
+}
+EXPORT_SYMBOL(set_bh_folio);
+
 /*
  * Called when truncating a buffer on a page completely.
  */
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 8f14dca5fed7..d5a2ef9b4cdf 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -196,6 +196,8 @@ void mark_buffer_write_io_error(struct buffer_head *bh);
 void touch_buffer(struct buffer_head *bh);
 void set_bh_page(struct buffer_head *bh,
 		struct page *page, unsigned long offset);
+void set_bh_folio(struct buffer_head *bh, struct folio *folio,
+		  unsigned long offset);
 bool try_to_free_buffers(struct folio *);
 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 		bool retry);
-- 
2.34.1