[PATCH 01/12] buffer: Add b_folio as an alias of b_page

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Buffer heads point to the allocation (ie the folio), not the page.
This is currently the same thing for all filesystems that use buffer
heads, so this is a safe transitional step.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/buffer_head.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 33fa5e94aa80..8f14dca5fed7 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -61,7 +61,10 @@ typedef void (bh_end_io_t)(struct buffer_head *bh, int uptodate);
 struct buffer_head {
 	unsigned long b_state;		/* buffer state bitmap (see above) */
 	struct buffer_head *b_this_page;/* circular list of page's buffers */
-	struct page *b_page;		/* the page this bh is mapped to */
+	union {
+		struct page *b_page;	/* the page this bh is mapped to */
+		struct folio *b_folio;	/* the folio this bh is mapped to */
+	};
 
 	sector_t b_blocknr;		/* start block number */
 	size_t b_size;			/* size of mapping */
-- 
2.35.1