linux-kernel - Re: [PATCH] f2fs: avoid unneeded preflush during checkpoint()

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Message-ID: <YgFvqnoa61BspqmW@google.com>
Date:   Mon, 7 Feb 2022 11:14:50 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <chao@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] f2fs: avoid unneeded preflush during checkpoint()

On 02/07, Chao Yu wrote:
> During checkpoint, we have committed preflush command via f2fs_flush_device_cache()

 787 int f2fs_flush_device_cache(struct f2fs_sb_info *sbi)
 788 {
 789         int ret = 0, i;
 790 
 791         if (!f2fs_is_multi_device(sbi))
 792                 return 0;

Seems a wrong assumption.

> to persist all metadata pages except last #2 CP pack page, so we don't need to
> commit another preflush command in commit_checkpoint(), remove it to avoid unneeded
> write cache overhead.
> 
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
>  fs/f2fs/data.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 8c417864c66a..15ac18bbbc8e 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -598,7 +598,7 @@ static void __f2fs_submit_merged_write(struct f2fs_sb_info *sbi,
>  		io->fio.op = REQ_OP_WRITE;
>  		io->fio.op_flags = REQ_META | REQ_PRIO | REQ_SYNC;
>  		if (!test_opt(sbi, NOBARRIER))
> -			io->fio.op_flags |= REQ_PREFLUSH | REQ_FUA;
> +			io->fio.op_flags |= REQ_FUA;
>  	}
>  	__submit_merged_bio(io);
>  	up_write(&io->io_rwsem);
> -- 
> 2.32.0