+ buffer-add-b_folio-as-an-alias-of-b_page.patch added to mm-unstable branch

+ buffer-add-b_folio-as-an-alias-of-b_page.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: buffer: add b_folio as an alias of b_page
has been added to the -mm mm-unstable branch.  Its filename is
     buffer-add-b_folio-as-an-alias-of-b_page.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/buffer-add-b_folio-as-an-alias-of-b_page.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: buffer: add b_folio as an alias of b_page
Date: Thu, 15 Dec 2022 21:43:51 +0000

Patch series "Start converting buffer_heads to use folios".

I was hoping that filesystems would convert from buffer_heads to iomap,
but that's not happening particularly quickly.  So the buffer_head
infrastructure needs to be converted from being page-based to being
folio-based.


This patch (of 12):

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.

Link: https://lkml.kernel.org/r/20221215214402.3522366-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20221215214402.3522366-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/buffer_head.h |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/include/linux/buffer_head.h~buffer-add-b_folio-as-an-alias-of-b_page
+++ a/include/linux/buffer_head.h
@@ -61,7 +61,10 @@ typedef void (bh_end_io_t)(struct buffer
 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 */
_

Patches currently in -mm which might be from willy@infradead.org are

buffer-add-b_folio-as-an-alias-of-b_page.patch
buffer-replace-obvious-uses-of-b_page-with-b_folio.patch
buffer-use-b_folio-in-touch_buffer.patch
buffer-use-b_folio-in-end_buffer_async_read.patch
buffer-use-b_folio-in-end_buffer_async_write.patch
page_io-remove-buffer_head-include.patch
buffer-use-b_folio-in-mark_buffer_dirty.patch
gfs2-replace-obvious-uses-of-b_page-with-b_folio.patch
jbd2-replace-obvious-uses-of-b_page-with-b_folio.patch
nilfs2-replace-obvious-uses-of-b_page-with-b_folio.patch
reiserfs-replace-obvious-uses-of-b_page-with-b_folio.patch
mpage-use-b_folio-in-do_mpage_readpage.patch