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Date:   Tue, 9 Nov 2021 08:39:53 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Jaegeuk Kim <jaegeuk@kernel.org>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net,
        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] f2fs: provide a way to attach HIPRI for Direct IO
Message-ID: <YYqkWWZZsMW49/xu@infradead.org>
References: <20211109021336.3796538-1-jaegeuk@kernel.org>
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In-Reply-To: <20211109021336.3796538-1-jaegeuk@kernel.org>
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On Mon, Nov 08, 2021 at 06:13:36PM -0800, Jaegeuk Kim wrote:
> This patch adds a way to attach HIPRI by expanding the existing sysfs's
> data_io_flag. User can measure IO performance by enabling it.

NAK.  This flag should only be used when explicitly specified by
the submitter of the I/O.

> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  Documentation/ABI/testing/sysfs-fs-f2fs | 16 +++++++++-------
>  fs/f2fs/data.c                          |  2 ++
>  fs/f2fs/f2fs.h                          |  3 +++
>  3 files changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index b268e3e18b4a..ac52e1c6bcbc 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -369,13 +369,15 @@ Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>
>  Description:	Give a way to attach REQ_META|FUA to data writes
>  		given temperature-based bits. Now the bits indicate:
>  
> -		+-------------------+-------------------+
> -		|      REQ_META     |      REQ_FUA      |
> -		+------+------+-----+------+------+-----+
> -		|    5 |    4 |   3 |    2 |    1 |   0 |
> -		+------+------+-----+------+------+-----+
> -		| Cold | Warm | Hot | Cold | Warm | Hot |
> -		+------+------+-----+------+------+-----+
> +		+------------+-------------------+-------------------+
> +		| HIPRI_DIO  |      REQ_META     |      REQ_FUA      |
> +		+------------+------+------+-----+------+------+-----+
> +		|          6 |    5 |    4 |   3 |    2 |    1 |   0 |
> +		+------------+------+------+-----+------+------+-----+
> +		|        All | Cold | Warm | Hot | Cold | Warm | Hot |
> +		+------------+------+------+-----+------+------+-----+
> +
> +		Note that, HIPRI_DIO bit is only for direct IO path.
>  
>  What:		/sys/fs/f2fs/<disk>/node_io_flag
>  Date:		June 2020
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 9f754aaef558..faa40aca2848 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -3707,6 +3707,8 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>  		if (do_opu)
>  			down_read(&fi->i_gc_rwsem[READ]);
>  	}
> +	if (sbi->data_io_flag & HIPRI_DIO)
> +		iocb->ki_flags |= IOCB_HIPRI;
>  
>  	err = __blockdev_direct_IO(iocb, inode, inode->i_sb->s_bdev,
>  			iter, rw == WRITE ? get_data_block_dio_write :
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index ce9fc9f13000..094f1e8ff82b 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1557,6 +1557,9 @@ struct decompress_io_ctx {
>  #define MAX_COMPRESS_LOG_SIZE		8
>  #define MAX_COMPRESS_WINDOW_SIZE(log_size)	((PAGE_SIZE) << (log_size))
>  
> +/* HIPRI for direct IO used in sysfs/data_io_flag */
> +#define HIPRI_DIO			(1 << 6)
> +
>  struct f2fs_sb_info {
>  	struct super_block *sb;			/* pointer to VFS super block */
>  	struct proc_dir_entry *s_proc;		/* proc entry */
> -- 
> 2.34.0.rc0.344.g81b53c2807-goog
> 
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