Re: [PATCH v3 02/12] nilfs2: drop usage of page_index

[Matthew Wilcox <willy@infradead.org>]

On Tue, Apr 30, 2024 at 03:04:50AM +0800, Kairui Song wrote:
> From: Kairui Song <kasong@tencent.com>
> 
> page_index is only for mixed usage of page cache and swap cache, for
> pure page cache usage, the caller can just use page->index instead.
> 
> It can't be a swap cache page here (being part of buffer head),
> so just drop it, also convert it to use folio.
> 
> Signed-off-by: Kairui Song <kasong@tencent.com>
> Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
> Cc: linux-nilfs@vger.kernel.org
> ---
>  fs/nilfs2/bmap.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nilfs2/bmap.c b/fs/nilfs2/bmap.c
> index 383f0afa2cea..f4e5df0cd720 100644
> --- a/fs/nilfs2/bmap.c
> +++ b/fs/nilfs2/bmap.c
> @@ -453,9 +453,8 @@ __u64 nilfs_bmap_data_get_key(const struct nilfs_bmap *bmap,
>  	struct buffer_head *pbh;
>  	__u64 key;
>  
> -	key = page_index(bh->b_page) << (PAGE_SHIFT -
> -					 bmap->b_inode->i_blkbits);
> -	for (pbh = page_buffers(bh->b_page); pbh != bh; pbh = pbh->b_this_page)
> +	key = bh->b_folio->index << (PAGE_SHIFT - bmap->b_inode->i_blkbits);
> +	for (pbh = folio_buffers(bh->b_folio); pbh != bh; pbh = pbh->b_this_page)
>  		key++;
>  
>  	return key;

Why isn't this entire function simply:

	return bh->b_blocknr;