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

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Date: Tue, 30 Apr 2024 03:22:10 +0800
From: Kairui Song <ryncsn@...il.com>
To: Matthew Wilcox <willy@...radead.org>
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 3:14 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> 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;
>

Nice idea, I didn't plan for extra clean up and test for fs code, but
this might be OK to have, will check it.