linux-ext4 - Re: [PATCH v2 4/9] jbd2: jump to new copy_done tag when b_frozen

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Message-ID: <20240514234246.3kspcjji4pjrwsnc@quack3>
Date: Wed, 15 May 2024 01:42:46 +0200
From: Jan Kara <jack@...e.cz>
To: Kemeng Shi <shikemeng@...weicloud.com>
Cc: tytso@....edu, jack@...e.com, yi.zhang@...weicloud.com,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/9] jbd2: jump to new copy_done tag when
 b_frozen_data is created concurrently

On Tue 14-05-24 19:24:33, Kemeng Shi wrote:
> If b_frozen_data is created concurrently, we can update new_folio and
> new_offset with b_frozen_data and then move forward
> 
> Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>

Looks good. Feel free to add:

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

								Honza

> ---
>  fs/jbd2/journal.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 714e2ef0115a..5fb5062cf7ae 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -351,7 +351,6 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
>  	atomic_set(&new_bh->b_count, 1);
>  
>  	spin_lock(&jh_in->b_state_lock);
> -repeat:
>  	/*
>  	 * If a new transaction has already done a buffer copy-out, then
>  	 * we use that version of the data for the commit.
> @@ -399,22 +398,22 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
>  		spin_lock(&jh_in->b_state_lock);
>  		if (jh_in->b_frozen_data) {
>  			jbd2_free(tmp, bh_in->b_size);
> -			goto repeat;
> +			goto copy_done;
>  		}
>  
>  		jh_in->b_frozen_data = tmp;
>  		memcpy_from_folio(tmp, new_folio, new_offset, bh_in->b_size);
> -
> -		new_folio = virt_to_folio(tmp);
> -		new_offset = offset_in_folio(new_folio, tmp);
> -		done_copy_out = 1;
> -
>  		/*
>  		 * This isn't strictly necessary, as we're using frozen
>  		 * data for the escaping, but it keeps consistency with
>  		 * b_frozen_data usage.
>  		 */
>  		jh_in->b_frozen_triggers = jh_in->b_triggers;
> +
> +copy_done:
> +		new_folio = virt_to_folio(jh_in->b_frozen_data);
> +		new_offset = offset_in_folio(new_folio, jh_in->b_frozen_data);
> +		done_copy_out = 1;
>  	}
>  
>  	/*
> -- 
> 2.30.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR