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

From: Dave Chinner
Date: Sat Oct 15 2016 - 03:59:22 EST


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@xxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> ---
> 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@xxxxxxxxxxxxx