linux-kernel - Re: [PATCH 5/6] fs: don't call ->writepage from __mpage

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Date:   Mon, 13 Jun 2022 12:53:02 +0200
From:   Jan Kara <jack@...e.cz>
To:     Christoph Hellwig <hch@....de>
Cc:     Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.com>,
        Dave Kleikamp <shaggy@...nel.org>,
        Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, jfs-discussion@...ts.sourceforge.net,
        ntfs3@...ts.linux.dev
Subject: Re: [PATCH 5/6] fs: don't call ->writepage from __mpage_writepage

On Mon 13-06-22 07:37:14, Christoph Hellwig wrote:
> All callers of mpage_writepage use block_write_full_page as their
> ->writepage implementation when called from mpage_writepages
> (although for ntfs3 this is obsfucated a bit).
> 
> Just call block_write_full_page directly instead of going through
> the ->writepage indirection.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>

Yeah, ntfs3 is not completely obvious but I agree we should not get to the
non-trivial case of ntfs_writepage() from mpage_writepages() now. Feel free
to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/mpage.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/mpage.c b/fs/mpage.c
> index 31a97a0acf5f5..a354ef2b4b4eb 100644
> --- a/fs/mpage.c
> +++ b/fs/mpage.c
> @@ -624,7 +624,7 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
>  	/*
>  	 * The caller has a ref on the inode, so *mapping is stable
>  	 */
> -	ret = mapping->a_ops->writepage(page, wbc);
> +	ret = block_write_full_page(page, mpd->get_block, wbc);
>  	mapping_set_error(mapping, ret);
>  out:
>  	mpd->bio = bio;
> -- 
> 2.30.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR