linux-ext4 - Re: [PATCH v4 10/13] ext4: Switch to using write_cache

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Message-ID: <20221208154046.s6aub2mhqfzewhuk@riteshh-domain>
Date:   Thu, 8 Dec 2022 21:10:46 +0530
From:   "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Ted Tso <tytso@....edu>, linux-ext4@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v4 10/13] ext4: Switch to using write_cache_pages() for
 data=journal writeout

On 22/12/07 12:27PM, Jan Kara wrote:
> Instead of using generic_writepages(), let's use write_cache_pages() for
> writeout of journalled data. It will allow us to stop providing
> .writepage callback.

Ok. Just one quick query. I didn't look too deep for this and thought will
directly check it here.
What about marking an error via mapping_set_error() which earlier the
__writepage() call was handling in case of any error during writeback?

> Our data=journal writeback path would benefit from
> a larger cleanup and refactoring but that's for a separate cleanup
> series.
>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext4/inode.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index b93a436bf5bc..f3b3792c1c96 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2705,6 +2705,12 @@ static int mpage_prepare_extent_to_map(struct mpage_da_data *mpd)
>  	return err;
>  }
>
> +static int ext4_writepage_cb(struct page *page, struct writeback_control *wbc,
> +			     void *data)
> +{
> +	return ext4_writepage(page, wbc);
> +}
> +
>  static int ext4_do_writepages(struct mpage_da_data *mpd)
>  {
>  	struct writeback_control *wbc = mpd->wbc;
> @@ -2731,7 +2737,9 @@ static int ext4_do_writepages(struct mpage_da_data *mpd)
>  		goto out_writepages;
>
>  	if (ext4_should_journal_data(inode)) {
> -		ret = generic_writepages(mapping, wbc);
> +		blk_start_plug(&plug);
> +		ret = write_cache_pages(mapping, wbc, ext4_writepage_cb, NULL);
> +		blk_finish_plug(&plug);
>  		goto out_writepages;
>  	}
>
> --
> 2.35.3
>