linux-ext4 - Re: [PATCH] ext4: don't mark mmp buffer head dirty

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Date:   Sun, 9 Sep 2018 22:57:35 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     Li Dongyang <dongyangli@....com>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: don't mark mmp buffer head dirty

On Sep 9, 2018, at 12:30 AM, Li Dongyang <dongyangli@....com> wrote:
> 
> Marking mmp bh dirty before writing it will make writeback
> pick up mmp block later and submit a write, we don't want the
> duplicate write as kmmpd thread should have full control of
> reading and writing the mmp block.
> Another reason is we will also have random I/O error on
> the writeback request when blk integrity is enabled, because
> kmmpd could modify the content of the mmp block(e.g. setting
> new seq and time) while the mmp block is under I/O requested
> by writeback.
> 
> Signed-off-by: Li Dongyang <dongyangli@....com>
> Cc: Andreas Dilger <adilger@...ger.ca>

Reviewed-by: Andreas Dilger <adilger@...ger.ca>

> ---
> fs/ext4/mmp.c | 1 -
> 1 file changed, 1 deletion(-)
> 
> diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c
> index 39b07c2d3384..2305b4374fd3 100644
> --- a/fs/ext4/mmp.c
> +++ b/fs/ext4/mmp.c
> @@ -49,7 +49,6 @@ static int write_mmp_block(struct super_block *sb, struct buffer_head *bh)
> 	 */
> 	sb_start_write(sb);
> 	ext4_mmp_csum_set(sb, mmp);
> -	mark_buffer_dirty(bh);
> 	lock_buffer(bh);
> 	bh->b_end_io = end_buffer_write_sync;
> 	get_bh(bh);
> --
> 2.18.0
> 


Cheers, Andreas






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