linux-kernel - Re: [PATCH 2/6] btrfs: drop usage of folio

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Message-ID: <30968c68-7ec2-4185-9b48-f8335dc2e0b0@gmx.com>
Date: Mon, 28 Apr 2025 10:24:38 +0930
From: Qu Wenruo <quwenruo.btrfs@....com>
To: Kairui Song <kasong@...cent.com>, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Matthew Wilcox <willy@...radead.org>, David Hildenbrand <david@...hat.com>,
 Hugh Dickins <hughd@...gle.com>, Chris Li <chrisl@...nel.org>,
 Yosry Ahmed <yosryahmed@...gle.com>,
 "Huang, Ying" <ying.huang@...ux.alibaba.com>, Nhat Pham <nphamcs@...il.com>,
 Johannes Weiner <hannes@...xchg.org>, linux-kernel@...r.kernel.org,
 Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
 David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org
Subject: Re: [PATCH 2/6] btrfs: drop usage of folio_index



在 2025/4/28 04:29, Kairui Song 写道:
> From: Kairui Song <kasong@...cent.com>
> 
> folio_index is only needed for mixed usage of page cache and swap
> cache, for pure page cache usage, the caller can just use
> folio->index instead.

The patch looks good to me, but I'm afraid the next commit message is 
not accurate.

> 
> It can't be a swap cache folio here.  Swap mapping may only call into fs
> through `swap_rw` and that is not supported for btrfs.  So just drop it
> and use folio->index instead.

Btrfs supports swap file, it's just not through the swap_rw() callback.

In this particular case, the folio belongs to the metadata (btree) 
inode, thus it will never be swap cache folio.

With that changed, it looks good to me.

Reviewed-by: Qu Wenruo <wqu@...e.com>

Thanks,
Qu

> 
> Signed-off-by: Kairui Song <kasong@...cent.com>
> Cc: Chris Mason <clm@...com> (maintainer:BTRFS FILE SYSTEM)
> Cc: Josef Bacik <josef@...icpanda.com> (maintainer:BTRFS FILE SYSTEM)
> Cc: David Sterba <dsterba@...e.com> (maintainer:BTRFS FILE SYSTEM)
> Cc: linux-btrfs@...r.kernel.org (open list:BTRFS FILE SYSTEM)
> Signed-off-by: Kairui Song <kasong@...cent.com>
> ---
>   fs/btrfs/extent_io.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 197f5e51c474..e08b50504d13 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -3509,7 +3509,7 @@ static void btree_clear_folio_dirty_tag(struct folio *folio)
>   	xa_lock_irq(&folio->mapping->i_pages);
>   	if (!folio_test_dirty(folio))
>   		__xa_clear_mark(&folio->mapping->i_pages,
> -				folio_index(folio), PAGECACHE_TAG_DIRTY);
> +				folio->index, PAGECACHE_TAG_DIRTY);
>   	xa_unlock_irq(&folio->mapping->i_pages);
>   }
>