Patch "buffer: make folio_create_empty_buffers() return a buffer_head" has been added to the 6.6-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    buffer: make folio_create_empty_buffers() return a buffer_head

to the 6.6-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     buffer-make-folio_create_empty_buffers-return-a-buff.patch
and it can be found in the queue-6.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit a527328a2fe173a7c65cf8e956f15fbd953cef49
Author: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Date:   Mon Oct 16 21:10:49 2023 +0100

    buffer: make folio_create_empty_buffers() return a buffer_head
    
    [ Upstream commit 3decb8564eff88a2533f83b01cec2cf9259c3eaf ]
    
    Patch series "Finish the create_empty_buffers() transition", v2.
    
    Pankaj recently added folio_create_empty_buffers() as the folio equivalent
    to create_empty_buffers().  This patch set finishes the conversion by
    first converting all remaining filesystems to call
    folio_create_empty_buffers(), then renaming it back to
    create_empty_buffers().  I took the opportunity to make a few
    simplifications like making folio_create_empty_buffers() return the head
    buffer and extracting get_nth_bh() from nilfs2.
    
    A few of the patches in this series aren't directly related to
    create_empty_buffers(), but I saw them while I was working on this and
    thought they'd be easy enough to add to this series.  Compile-tested only,
    other than ext4.
    
    This patch (of 26):
    
    Almost all callers want to know the first BH that was allocated for this
    folio.  We already have that handy, so return it.
    
    Link: https://lkml.kernel.org/r/20231016201114.1928083-1-willy@xxxxxxxxxxxxx
    Link: https://lkml.kernel.org/r/20231016201114.1928083-3-willy@xxxxxxxxxxxxx
    Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
    Reviewed-by: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
    Cc: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
    Cc: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
    Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Stable-dep-of: 367a9bffabe0 ("nilfs2: protect access to buffers with no active references")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/buffer.c b/fs/buffer.c
index ecd8b47507ff8..4b86e971efd8a 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1640,8 +1640,8 @@ EXPORT_SYMBOL(block_invalidate_folio);
  * block_dirty_folio() via private_lock.  try_to_free_buffers
  * is already excluded via the folio lock.
  */
-void folio_create_empty_buffers(struct folio *folio, unsigned long blocksize,
-				unsigned long b_state)
+struct buffer_head *folio_create_empty_buffers(struct folio *folio,
+		unsigned long blocksize, unsigned long b_state)
 {
 	struct buffer_head *bh, *head, *tail;
 
@@ -1667,6 +1667,8 @@ void folio_create_empty_buffers(struct folio *folio, unsigned long blocksize,
 	}
 	folio_attach_private(folio, head);
 	spin_unlock(&folio->mapping->private_lock);
+
+	return head;
 }
 EXPORT_SYMBOL(folio_create_empty_buffers);
 
@@ -1768,13 +1770,15 @@ static struct buffer_head *folio_create_buffers(struct folio *folio,
 						struct inode *inode,
 						unsigned int b_state)
 {
+	struct buffer_head *bh;
+
 	BUG_ON(!folio_test_locked(folio));
 
-	if (!folio_buffers(folio))
-		folio_create_empty_buffers(folio,
-					   1 << READ_ONCE(inode->i_blkbits),
-					   b_state);
-	return folio_buffers(folio);
+	bh = folio_buffers(folio);
+	if (!bh)
+		bh = folio_create_empty_buffers(folio,
+				1 << READ_ONCE(inode->i_blkbits), b_state);
+	return bh;
 }
 
 /*
@@ -2678,10 +2682,8 @@ int block_truncate_page(struct address_space *mapping,
 		return PTR_ERR(folio);
 
 	bh = folio_buffers(folio);
-	if (!bh) {
-		folio_create_empty_buffers(folio, blocksize, 0);
-		bh = folio_buffers(folio);
-	}
+	if (!bh)
+		bh = folio_create_empty_buffers(folio, blocksize, 0);
 
 	/* Find the buffer that contains "offset" */
 	offset = offset_in_folio(folio, from);
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 44e9de51eedfb..572030db2f061 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -203,8 +203,8 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
 		bool retry);
 void create_empty_buffers(struct page *, unsigned long,
 			unsigned long b_state);
-void folio_create_empty_buffers(struct folio *folio, unsigned long blocksize,
-				unsigned long b_state);
+struct buffer_head *folio_create_empty_buffers(struct folio *folio,
+		unsigned long blocksize, unsigned long b_state);
 void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
 void end_buffer_write_sync(struct buffer_head *bh, int uptodate);
 void end_buffer_async_write(struct buffer_head *bh, int uptodate);