linux-kernel - Re: [PATCH] DAX: enable iostat for read/write

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Date:   Sat, 15 Oct 2016 18:54:43 +1100
From:   Dave Chinner <david@...morbit.com>
To:     Toshi Kani <toshi.kani@....com>
Cc:     akpm@...ux-foundation.org, dan.j.williams@...el.com,
        viro@...iv.linux.org.uk, ross.zwisler@...ux.intel.com,
        linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] DAX: enable iostat for read/write

On Fri, Oct 14, 2016 at 11:25:13AM -0600, Toshi Kani wrote:
> DAX IO path does not support iostat, but its metadata IO path does.
> Therefore, iostat shows metadata IO statistics only, which has been
> confusing to users.
> 
> Add iostat support to the DAX read/write path.
> 
> Note, iostat still does not support the DAX mmap path as it allows
> user applications to access directly.
> 
> Signed-off-by: Toshi Kani <toshi.kani@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
> ---
>  fs/dax.c |   37 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 37 insertions(+)
> 
> diff --git a/fs/dax.c b/fs/dax.c
> index 014defd..3aaaac2 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -144,6 +144,34 @@ static sector_t to_sector(const struct buffer_head *bh,
>  	return sector;
>  }
>  
> +static void dax_iostat_start(struct gendisk *disk, struct iov_iter *iter,
> +			     unsigned long *start)
> +{
> +	int rw = iov_iter_rw(iter);
> +	int sec = iov_iter_count(iter) >> 9;
> +	int cpu = part_stat_lock();
> +
> +	*start = jiffies;
> +	part_round_stats(cpu, &disk->part0);
> +	part_stat_inc(cpu, &disk->part0, ios[rw]);
> +	part_stat_add(cpu, &disk->part0, sectors[rw], sec);
> +	part_inc_in_flight(&disk->part0, rw);
> +	part_stat_unlock();
> +}

Why reimplement generic_start_io_acct() and generic_end_io_acct()?

-Dave.
-- 
Dave Chinner
david@...morbit.com