linux-ext4 - Re: [PATCH 4/9] ext4: Drop pointless IO submission from ext4_bio_write

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Date:   Thu, 1 Dec 2022 12:36:55 +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>
Subject: Re: [PATCH 4/9] ext4: Drop pointless IO submission from
 ext4_bio_write_page()

On 22/11/30 05:35PM, Jan Kara wrote:
> We submit outstanding IO in ext4_bio_write_page() if we find a buffer we
> are not going to write. This is however pointless because we already
> handle submission of previous IO in case we detect newly added buffer
> head is discontiguous. So just delete the pointless IO submission call.

Agreed. io_submit_add_bh() is anyway called at the end for submitting buffers.
And io_submit_add_bh() also has the logic to:
1. submit a discontiguous bio
2. Also submit a bio if the bio gets full (submit_and_retry label).

Hence calling ext4_io_submit() early is not required.

I guess the same will also hold true for at this place.
https://elixir.bootlin.com/linux/v6.1-rc7/source/fs/ext4/page-io.c#L524


But this patch looks good to me. Feel free to add:
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>



>
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  fs/ext4/page-io.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 2bdfb8a046d9..beaec6d81074 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -489,8 +489,6 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
>  					redirty_page_for_writepage(wbc, page);
>  				keep_towrite = true;
>  			}
> -			if (io->io_bio)
> -				ext4_io_submit(io);
>  			continue;
>  		}
>  		if (buffer_new(bh))
> --
> 2.35.3
>