linux-kernel - Re: [PATCH v3 02/12] nilfs2: drop usage of page

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Date: Mon, 29 Apr 2024 20:14:00 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Kairui Song <kasong@...cent.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	"Huang, Ying" <ying.huang@...el.com>, Chris Li <chrisl@...nel.org>,
	Barry Song <v-songbaohua@...o.com>,
	Ryan Roberts <ryan.roberts@....com>, Neil Brown <neilb@...e.de>,
	Minchan Kim <minchan@...nel.org>, Hugh Dickins <hughd@...gle.com>,
	David Hildenbrand <david@...hat.com>,
	Yosry Ahmed <yosryahmed@...gle.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Ryusuke Konishi <konishi.ryusuke@...il.com>,
	linux-nilfs@...r.kernel.org
Subject: Re: [PATCH v3 02/12] nilfs2: drop usage of page_index

On Tue, Apr 30, 2024 at 03:04:50AM +0800, Kairui Song wrote:
> From: Kairui Song <kasong@...cent.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@...cent.com>
> Cc: Ryusuke Konishi <konishi.ryusuke@...il.com>
> Cc: linux-nilfs@...r.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;